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Telecom Dictionary - Definitions of terms



E-1 - The European equivalent of a T-1.

E1 (or E-1) - A European digital transmission format devised by the ITU-TS and given the name by the Conference of European Postal and Telecommunication Administration (CEPT). It's the equivalent of the North American T-carrier system format. E2 through E5 are carriers in increasing multiples of the E1 format.

The E1 signal format carries data at a rate of 2.048 million bits per second and can carry 32 channels of 64 Kbps* each. E1 carries at a somewhat higher data rate than T-1 (which carries 1.544 million bits per second) because, unlike T-1, it does not do bit-robbing and all eight bits per channel are used to code the signal. E1 and T-1 can be interconnected for international use.

E2 (E-2) - A line that carries four multiplexed E1 signals with a data rate of 8.448 million bits per second.

E3 (E-3) - A line that carries 16 E1 signals with a data rate of 34.368 million bits per second.

E4 (E-4) - A line that carries four E3 channels with a data rate of 139.264 million bits per second.

E5 (E-5) - A line that carries four E4 channels with a data rate of 565.148 million bits per second.

E911 - Technology allowing 911 calls from cellular phones to be routed to the geographically correct emergency station (a.k.a. PSAP: Public Safety Answering Point). VoIP users currently have limited access to 911 services, and with some providers none, because VoIP is not geographically based.

In the United States, E911 (Enhanced 911) is support for wireless phone users who dial 911, the standard number for requesting help in an emergency. Since wireless users are often mobile, some sort of enhancement is needed to 911 service that allows the location of the user to be known to the call receiver. E911 support is mandated by the U.S. Federal Communications Commission (FCC) for traditional mobile phone service and, since May 19, 2005, for certain VoIP service. Phase 1 of the E911 program required a service provider to provide the telephone number of a 911 caller and the location of the antenna receiving the call to a local Public Safety Answering Point (PSAP). Phase 2 requires the provider to furnish more precise information about the caller's location, usually to within 50 to 300 meters. Phase 2, which requires new technology, is to be completed by the end of 2005.

On May 19, 2005, the FCC also required that Internet service providers who interconnect VoIP calls with the public switched telephone network (PSTN) must provide E911 service for these callers and call dispatchers. Providers are required to inform users of the capabilities and any limitations of their 911 service. Providers were given 120 days to comply. Previously, as a general policy, the FCC had taken a "hands-off" position about regulating Internet traffic on the argument that the Internet is an information service rather than a communications service. Providers do not have to furnish E911 service for VoIP callers who do not interconnect with the PSTN such as those using instant messaging and Internet gaming.

E911 Taxes/Surcharges - This tax is set and imposed by local governments to help pay for the cost of an emergency response communications system that identifies both the caller and the location of the call.

Ear and mouth (E&M) - A technology in voice over IP (VoIP) that uses a traditional telephone handset with an earphone (or earpiece) for listening to incoming audio and a microphone (or mouthpiece) for transmitting audio. Calls using an E&M interface can be made from, received from, or disconnected by a private branch exchange (PBX) as well as from a VoIP-capable computer.

The main advantage of E&M is the fact that it allows a PBX to reliably detect disconnect (hang-up) signals. This eliminates problems that can otherwise occur with locked computer ports at the terminations of calls, and thus minimizes the risk of needlessly consuming network resources.

The term ear and mouth interface is sometimes used as a synonym for a telephone handset itself, or for a headset-and-microphone combination that allows hands-free operation.

Earth Electrode Subsystem - A network of electrically interconnected rods, plates, mats, or grids, installed and connected, for the purpose of establishing a low-resistance contact with earth.

Earth Ground - See ground. - 1. An electrical connection to earth through an earth-electrode subsystem. 2. In an electrical circuit, a common return path that usually (a) is connected to an earth-electrode subsystem and (b) is extended throughout a facility via a facility ground system consisting of the signal reference subsystem, the fault protection subsystem, and the lightning protection subsystem. 3. In an electrical circuit, a common return path that (a) may not necessarily be connected to earth and (b) is the zero voltage reference level for the equipment or system.

EAS - 1. Extended Area Service. Customers usually pay a larger flat rate to increase their local calling area if an area gets EAS. It can decrease a customer’s monthly bill if the customer makes a certain number of calls to the expanded area. 2. Emergency Alert System. This is designed to provide the President with a means to address the American people in the event of a national emergency.

E-carrier - System, where 'E' stands for European, is incompatible with the T-carrier and is used just about everywhere else in the world besides North America and Japan. It typically uses the E1 line rate and the E3 line rate. The E2 line rate is less commonly used. A European digital transmission format devised by the ITU-TS and given the name by the Conference of European Postal and Telecommunication Administration (CEPT). It's the equivalent of the North American T-carrier system format. E2 through E5 are carriers in increasing multiples of the E1 format.

Echo - 1. A wave that has been reflected by a discontinuity in the propagation medium. 2. A wave that has been reflected or otherwise returned with sufficient magnitude and delay to be perceived. Note 1: Echoes are frequently measured in dB relative to the directly transmitted wave. Note 2: Echoes may be desirable (as in radar ) or undesirable (as in telephone systems). 3. In computing, to print or display characters (a) as they are entered from an input device, (b) as instructions are executed, or (c) as retransmitted characters received from a remote terminal. 4. In computer graphics, the immediate notification of the current values provided by an input device to the operator at the display console.

Echo Check - A check to determine the integrity of transmission of data, whereby the received data are returned to the source for comparison with the originally transmitted data. Synonym loop check.

EDI - (Electronic Data Interchange) - The electronic communication of business transactions, such as orders, confirmations and invoices, between organizations. Third parties provide EDI services that enable organizations with different equipment to connect. Although interactive access may be a part of it, EDI implies direct computer to computer transactions into vendors' databases and ordering systems.

The Internet has given EDI quite a boost, but not by using private networks and the traditional EDI data formats (X12, EDIFACT and TRADACOMS). Rather, XML has been the glue that connects businesses together using the Web as the communications vehicle.

Edge-Emitting LED - An LED that has a physical structure superficially resembling that of an injection laser diode, operated below the lasing threshold and emitting incoherent light. Note: Edge-emitting LEDs have a relatively small beam divergence, and thus are capable of launching more optical power into a given fiber than are the conventional surface-emitting LEDs.

EDTV - Enhanced Definition TV. A better digital television transmission than SDTV with at least 480p (progressive), in a 16:9 or 4:3 display and Dolby® digital surround sound. The quality of most progressive scan DVDs and players is 480p.

Effective Radiated Power (e.r.p.) (in a given direction) - 1. The power supplied to an antenna multiplied by the antenna gain in a given direction. Note 1: If the direction is not specified, the direction of maximum gain is assumed. Note 2: The type of reference antenna must be specified. 2. The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction. Note: If the direction is not specified, the direction of maximum gain is assumed. 3. The effective radiated power of a transmitter (with antenna, transmission line, duplexers, etc.,) is the power that would be necessary at the input terminals of a reference half-wave dipole antenna in order to produce the same maximum field intensity. ERP is usually calculated by multiplying the measured transmitter output power by the specified antenna system gain, relative to a half-wave dipole, in the direction of interest.

Electrical Plugs and Sockets -

When electricity was first introduced into the domestic environment it was primarily for lighting. However, as it became a viable alternative to other means of heating and also the development of labour saving appliances, a means of connection to the supply other than via a light socket was required. In the 1920s, the two-prong plug made its appearance.

At that time, some electricity companies operated a split tariff system where the cost of electricity for lighting was lower than that for other purposes, which led to low wattage appliances (e.g. vacuum cleaners, hair dryers, etc.) being connected to the light fitting. The picture below shows a 1909 electric toaster with a lightbulb socket plug.


early light fitting plug with antque toaster


As the need for safer installations grew, three-pin outlets were developed. The third pin on the outlet was an earth pin, which was effectively connected to earth, this being at the same potential as the neutral supply line. The idea behind it was that in the event of a short circuit to earth, a fuse would blow, thus disconnecting the supply.

The reason why we are now stuck with no less than 13 different styles of plugs and wall outlets, is because many countries preferred to develop a plug of their own, instead of adopting the US standard. Moreover, the plugs and sockets are only very rarely compatible, which makes it often necessary to replace the plug when you buy appliances abroad.

Below is a brief outline of the plugs and sockets used around the world in domestical environment.



(used in, among others, North and Central America and Japan)
Type A Electric Plug

This class II ungrounded plug with two flat parallel prongs is pretty much standard in most of North and Central America. At first glance, the Japanese plug and socket seem to be identical to this standard. However, the Japanese plug has two identical flat prongs, whereas the US plug has one prong which is slightly larger. Therefore it is no problem to use Japanese plugs in the US, but the opposite does not work often. Furthermore, Japanese standard wire sizes and the resulting current ratings are different than those used on the American continent.

Type A and B plugs have two flat prongs with a hole near the tip. These holes aren't there without a reason. If you were to take apart a type A or B socket and look at the contact wipers that the prongs slide into, you would find that in some cases they have have bumps on them. These bumps fit into the holes so that the outlet can grip the plug’s prongs more firmly. This prevents the plug from slipping out of the socket due to the weight of the plug and cord. It also improves the contact between the plug and the outlet. Some sockets, however, don't have those bumps but just two spring-action blades that grip the sides of the plug pin, in which case the holes aren't necessary.

There are also some special outlets which allow you to lock the cord into the socket, by putting rods through the holes. This way, for example vending machines cannot be unplugged. Moreover, electrical devices can be "factory-sealed" by the manufacturer using a plastic tie or a small padlock through one or both of the plug prong holes. For example, a manufacturer might apply a plastic band through the hole and attach it to a tag that says: "You must do X or Y before plugging in this device". The user cannot plug in the device without removing the tag, so the user is sure to see the tag.



(used in, among others, North and Central America and Japan)
Type B Electrical Plug

This is a class I plug with two flat parallel prongs and a grounding pin (American standard NEMA 5-15/Canadian standard CS22.2, n°42). It is rated at 15 amps and although this plug is also standard in Japan, it is less frequently used than in North America. Consequently, most appliances sold in Japan use a class II ungrounded plug. As is the case with the type A standard, the Japanese type B plugs and sockets are slightly different from their American counterparts.

An ungrounded version of the North American NEMA 5-15 plug is commonly used in Central America and parts of South America. It is therefore common for equipment users to simply cut off the grounding pin that the plug can be mated with a two-pole ungrounded socket.




  (used in all countries of Europe except the United Kingdom, Ireland, Cyprus and Malta)
  Type C Electrical Plug
  This two-wire plug is ungrounded and has two round prongs. It is popularly known as the europlug which is described in CEE 7/16. This is probably the single most widely used international plug. It will mate with any socket that accepts 4.0-4.8 mm round contacts on 19 mm centres. It is commonly used in all countries of Europe except the United Kingdom and Ireland. It is also used in various parts of the developing world. This plug is generally limited for use in class II applications that require 2.5 amps or less. It is, of course, unpolarised.



(used almost exclusively in India, Sri Lanka, Nepal and Namibia)
Type D Electrical Plug

India has standardised on a plug which was originally defined in British Standard 546 (the standard in Great Britain before 1962). This plug has three large round pins in a triangular pattern. It is rated at 5 amps. Type M, which has larger pins and is rated at 15 amps, is used alongside type D for larger appliances in India, Sri Lanka, Nepal and Namibia. Some sockets can take both type M and type D plugs.

Although type D is now almost exclusively used in India, Sri Lanka, Nepal and Namibia, it can still occasionally be found in hotels and theatres in the UK and Ireland. It should be noted that tourists should not attempt to connect anything to a BS546 round-pin outlet found in the UK or Ireland as it is likely to be on a circuit that has a special purpose: e.g. for providing direct current (DC) or for plugging in lamps that are controlled by a light switch or a dimmer.



(primarily used in France, Belgium, Poland, Slovakia, the Czech Republic, Tunisia and Morocco)
Type E Electrical Plug
France, Belgium and some other countries have standardised on a socket which is different from the CEE 7/4 socket (type F) that is standard in Germany and other continental European countries. The reason for incompatibility is that grounding in the E socket is accomplished with a round male pin permanently mounted in the socket. The plug itself is similar to C except that it is round and has the addition of a female contact to accept the grounding pin in the socket. In order to bridge the differences between sockets E and F, the CEE 7/7 plug was developed: it has grounding clips on both sides to mate with the type F socket and a female contact to accept the grounding pin of the type E socket. The original type E plug, which does not have grounding clips, is no longer used, although very rarely it can still be found on some older appliances. Note that the CEE 7/7 plug is polarised when used with a type E outlet. The plug is rated at 16 amps. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 309 system. A type C plug fits perfectly into a type E socket.



(used in, among others, Germany, Austria, the Netherlands, Sweden, Norway, Finland, Portugal, Spain and Eastern Europe)
Type F Electric Plug

Plug F, known as CEE 7/4 and commonly called "Schuko plug", is similar to C except that it is round and has the addition of two grounding clips on the side of the plug. It has two 4.8 mm round contacts on 19 mm centres. Because the CEE 7/4 plug can be inserted in either direction into the receptacle, the Schuko connection system is unpolarised (i.e. line and neutral are connected at random). It is used in applications up to 16 amps. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 309 system. In order to bridge the differences between sockets E and F, the CEE 7/7 plug was developed. This plug, which is shown above, has grounding clips on both sides to mate with the type F socket and a female contact to accept the grounding pin of the type E socket. The original type F plug, which does not have this female contact, is still available at the DIY shops but only in a rewireable version. A type C plug fits perfectly into a type F socket.

The Soviet Republics use a standard plug and socket defined in Russian Standard Gost 7396 which is similar to the Schuko standard. Contacts are also on 19 mm centres, but the diameter of this contact is 4.0 mm compared to 4.8 mm which is standard in Continental Europe. It is possible to mate Russian plugs with Schuko outlets, but Russian sockets will not allow to connect type E and F plugs as the outlets have smaller hole diameters than the pins of those two plugs mentioned. Many official standards in Eastern Europe are virtually identical to the Schuko standard. Furthermore, one of the protocols governing the reunification of Germany provided that the DIN and VDE standards would prevail without exception. The former East Germany was required to confirm to the Schuko standard. It appears that most if not all of the Eastern European countries generally use the Schuko standard internally but, until recently, they exported appliances to the Soviet Union with the Soviet standard plug installed. Because the volumes of appliance exports to the Soviet Union were large, the Soviet plug has found its way into use in Eastern Europe as well.



(mainly used in the United Kingdom, Ireland, Cyprus, Malta, Malaysia and Singapore)
Type G Electrical Plug

This plug has three rectangular prongs that form a triangle. British Standard BS 1363 requires use of a three-wire grounded and fused plug for all connections to the power mains (including class II, two-wire appliances). British power outlets incorporate shutters on line and neutral contacts to prevent someone from pushing a foreign object into the socket.

The British domestic electrical system uses a ring circuit in the building which is rated for 32 amps (6 amps for lighting circuits). Moreover, there is also a fusing in the plug; a cartridge fuse, usually of 3 amps for small appliances like radios etc. and 13 amps for heavy duty appliances such as heaters. Almost everywhere else in the world a spur main system is used. In this system each wall socket, or group of sockets, has a fuse at the main switchboard whereas the plug has none. So if you take some foreign appliance to the UK, you can use an adaptor, but technically it must incorporate the correct value fuse. Most would have a 13 amps one, too big for the computer for example. BS 1363 was published in 1962 and since that time it has gradually replaced the earlier standard plugs and sockets (type D) (BS 546).



(used exclusively in Israel)
Type H Electrical Plug
This plug, defined in SI 32, is unique to Israel. It has two flat prongs like the type B plug, but they form a V-shape rather than being parallel like B plugs. Type H plugs have got a grounding pin as well and are rated at 16 amps. Type H sockets are so shaped as to accommodate type C plugs as well. The slots for the non-grounded prongs have widenings in the middle specifically to allow type C prongs to fit in.



(mainly used in Australia, New Zealand, Papua New Guinea and Argentina)
Type I Electrical Plug

This plug has also a grounding pin and two flat prongs forming a V-shape. There is an ungrounded version of this plug as well, with only two flat V-shaped prongs. Although the above plug looks very similar to the one used in Israel (type H), both plugs are not compatible. Australia’s standard plug/socket system is described in SAA document AS 3112 and is used in applications up to 10 amps. A plug/socket configuration with rating at 15 amps (ground pin is wider: 8 mm instead of 6.35 mm) is also available. A standard 10 amp plug will fit into a 15 amp outlet, but a 15 amp plug only fits this special 15 amp socket. There is also a 20 amp plug whose earth blade is wider still. A lower-amperage plug will always fit into a higher-amperage outlet but not vice versa. Although there are slight differences, the Australian plug mates with the socket used in the People's Republic of China (mainland China).



(used almost exclusively in Switzerland, Liechtenstein and Brazil)
Type J Electrical Plug
Switzerland has its own standard which is described in SEC 1011. This plug is similar to C, except that it has the addition of a grounding pin. This connector system is rated for use in applications up to 10 amps. Above 10 amps, equipment must be either wired permanently to the electrical supply system with appropriate branch circuit protection or connected to the mains with an appropriate high power industrial connector. Type J is also the official grounded standard in Brazil, as described in NBR 14136. A type C plug fits perfectly into a type J socket.



(used almost exclusively in Denmark and Greenland)
Type K Electrical Plug
The Danish standard is described in Afsnit 107-2-D1. The plug is similar to F except that it has a grounding pin instead of grounding clips. The Danish socket will also accept either the CEE 7/4 or CEE 7/7 plugs: however, there is no grounding connection with these plugs because a male ground pin is required on the plug. The correct plug must be used in Denmark for safety reasons. A variation of this plug intended for use only on surge protected computer circuits has been introduced. The current rating on both plugs is 10 amps. A type C plug fits perfectly into a type K socket.



(used almost exclusively in Italy and randomly found throughout North Africa)
Type L Electrical Plug
The Italian grounded plug/socket standard, CEI 23-16/VII, includes two styles rated at 10 and 16 amps. They differ in terms of contact diameter and spacing, and are therefore incompatible with each other. The plugs are similar to C except that they are earthed by means of a centre grounding pin. Because they can be inserted in either direction at random, they are unpolarised. A type C plug fits perfectly into a type L socket.



(used almost exclusively in South Africa, Swaziland and Lesotho)
This plug resembles the Indian type D plug, but its pins are much larger. Type M is rated at 15 amps. Although type D is standard in India, Sri Lanka, Nepal and Namibia, type M is also used for larger appliances. Some sockets over there can take both type M and type D plugs.


Afghanistan C / F
Albania C / F
Algeria C / F
American Samoa A / B / F / I
Andorra C / F
Angola C
Anguilla A
Antigua A / B
Argentina C / I*
Armenia C / F
Aruba A / B / F
Australia I
Austria C / F
Azerbaijan C
Azores B / C / F
Bahamas A / B
Bahrain G
Balearic Islands C / F
Bangladesh A / C / D / G / K
Barbados A / B
Belarus C
Belgium E
Belize B / G
Benin E
Bermuda A / B
Bhutan D / F / G
Bolivia A / C
Bosnia & Herzegovina C / F
Botswana D / G
Brazil A / B / C / I / J**
Brunei G
Bulgaria C / F
Burkina Faso C / E
Burundi C / E
Cambodia A / C / G
Cameroon C / E
Canada A / B
Canary Islands C / E / L
Cape Verde C / F
Cayman Islands A / B
Central African Republic C / E
Chad D / E / F
Channel Islands C / G
Chile C / L
China, People's Republic of A / I / G
Colombia A / B
Comoros C / E
Congo, People's Rep. of C / E
Congo, Dem. Rep. of (formerly Zaire) C / D
Cook Islands I
Costa Rica A / B
Côte d'Ivoire 
(Ivory Coast)
C / E
Croatia C / F
Cuba A / B / C / L
Cyprus G / F***
Czech Republic E
Denmark C / K
Djibouti C / E
Dominica D / G
Dominican Republic A / B
East Timor C / E / F / I
Ecuador A / B
Egypt C
El Salvador A / B / C / D / E / F / G / I / J / L
Equatorial Guinea C / E
Eritrea C
Estonia F
Ethiopia C / F
Faeroe Islands C / K
Falkland Islands G
Fiji I
Finland C / F
France E
French Guyana C / D / E
Gabon C
Gambia G
Gaza H
Georgia C
Germany C / F
Ghana D / G
Gibraltar C / G
Greece C / F
Greenland C / K
Grenada (Windward Islands) G
Guadeloupe C / D / E
Guam A / B
Guatemala A / B / G / I
Guinea C / F / K
Guinea-Bissau C
Guyana A / B / D / G
Haiti A / B
Honduras A / B
Hong Kong D / M / G
Hungary C / F
Iceland C / F
India C / D / M
Indonesia C / F / G
Iran C / F
Iraq C / D / G
Ireland (Eire) G
Isle of Man C / G
Israel H / C
Italy F / L
Jamaica A / B
Japan A / B
Jordan B / C / D / F / G / J
Kenya G
Kazakhstan C
Kiribati I
Korea, South C / F
Kuwait C / G
Kyrgyzstan C
Laos A / B / C / E / F
Latvia C / F
Lebanon A / B / C / D / G
Lesotho M
Liberia A / B
Libya D
Liechtenstein J
Lithuania C / E
Luxembourg C / F
Macau D / G
Macedonia C / F
Madagascar C / D / E / J / K
Madeira C / F
Malawi G
Malaysia G
Maldives A / D / G / J / K / L
Mali C / E
Malta G
Martinique C / D / E
Mauritania C
Mauritius C / G
Mexico A
Micronesia, Federal States of A / B
Moldova C
Monaco C / D / E / F
Mongolia C / E
Montserrat (Leeward Islands) A / B
Morocco C / E
Mozambique C / F / M
Myanmar (formerly Burma) C / D / F / G
Namibia D / M
Nauru I
Nepal C / D / M
Netherlands C / F
Netherlands Antilles A / B / F
New Caledonia F
New Zealand I
Nicaragua A
Niger A / B / C / D / E / F
Nigeria D / G
Norway C / F
Oman C / G
Pakistan C / D
Palau A / B
Panama A / B
Papua New Guinea I
Paraguay C
Peru A / B / C
Philippines A / B / C
Poland C / E
Portugal C / F
Puerto Rico A / B
Qatar D / G
Réunion Island E
Romania C / F
Russian Federation C / F
Rwanda C / J
St. Kitts and Nevis (Leeward Islands) D / G
St. Lucia (Windward Islands) G
St. Vincent (Windward Islands) A / C / E / G / I / K
San Marino F / L
Saudi Arabia A / B / C / G
Senegal C / D / E / K
Serbia & Montenegro C / F
Seychelles G
Sierra Leone D / G
Singapore G
Slovakia E
Slovenia C / F
Somalia C
South Africa M****
Spain C / F
Sri Lanka D / M
Sudan C / D
Suriname C / F
Swaziland M
Sweden C / F
Switzerland J
Syria C / E / L
Tahiti A / B / E
Tajikistan C / I
Taiwan A / B
Tanzania D / G
Thailand A / C
Togo C
Tonga I
Trinidad & Tobago A / B
Tunisia C / E
Turkey C / F
Turkmenistan B / F
Uganda G
Ukraine C / F
United Arab Emirates G
United Kingdom G
United States of America A / B
Uruguay C / F / I / L
Uzbekistan C / I
Venezuela A / B
Vietnam A / C / G
Virgin Islands (British and U.S.) A / B
Western Samoa I
Yemen, Rep. of A / D / G
Zambia C / D / G
Zimbabwe D / G

* Argentina has standardised on type I sockets and plugs. Type C plugs and power points are still commonly found in older buildings.

** Although many types of plugs and receptacles are used all over Brazil, only type J plugs and sockets are allowed. Type C plugs (NOT type C sockets !) are authorised as well.

*** Type G plugs and sockets are used in the north as well as the south of Cyprus, whereas type F plugs and receptacles are only found in the north of the island.

**** The official South African socket and plug standard is type M. Nevertheless, appliances with a type C plug are still very commonly found and used with a plug adapter.

The outline map below visualises the spread of the different plug types used around the world. For easy reference, compatible plug types are represented with the same colour.

World Electrical Plug Types


What do I need to use my appliances abroad ?

Plug Adapters

They do not convert electricity. They simply allow a dual-voltage appliance, a transformer or a converter from one country to be plugged into the wall outlet of another country. The plug of a Continental European appliance will not fit into an outlet in a foreign country without an adapter.


Converters and transformers both step up or down the voltage, but there is a difference in use between them. Converters should be used only with "electric" products. Electric products are simple heating devices or have mechanical motors. Examples are hair dryers, steam irons, shavers, toothbrushes or small fans. Converters are not designed for "continuous duty" and should only be used for short periods of time (1 to 2 hours). Additionally, most converters can only be used for ungrounded appliances (2 pins on the plug). Converters must be unplugged from the wall when not in use.


Transformers also step up or down the voltage, but they are more expensive than converters and are used with "electronic" products. Electronic products have a chip or circuit. Examples are radios, CD or DVD players, shavers, camcorder battery rechargers, computers, computer printers, fax machines, televisions and answering machines. Transformers can also be used with electric appliances and may be operated continually for many days. The advantage of converters, however, is that they are lighter and less expensive.

Computers are electronic devices and therefore they must be used with a transformer, unless they are dual voltage. Fortunately, most laptop battery chargers and AC adapters are dual voltage, so they can be used with only a plug adapter for the country you will be visiting.

Transformers are sold in various sizes based on how much wattage they can support. Therefore one must pay careful attention to the wattage ratings of the appliances to be plugged into a transformer. The wattage rating of the transformer must always be larger than the wattage rating of the appliance to be plugged into it (plus a 25% buffer to allow for heat build-up in the transformer or converter). When plugging multiple items into a power strip, then into the transformer, you must calculate the combined wattage of all appliances and the power strip, then add an additional 25% to that total.

The appliance’s voltage and wattage requirements are listed on the manufacturer's label located on the back or at the bottom of the appliance. In some cases, the voltage and amperage will be listed, but not the wattage. If this is the case, simply multiply the voltage by the amperage rating to find the wattage rating (e.g. 230 V * 1 A = 230 W).

Below is a list that gives an idea what the wattage of common appliances is. Use this as a guide only. Always check your appliance first !

Transformers and converters only convert the voltage, not the frequency. The difference in cycles may cause the motor in a 50 Hz appliance to operate slightly faster when used on 60 Hz electricity. This cycle difference will cause electric clocks and timing circuits to keep incorrect time: European alarm clocks will run faster on 60 Hz electricity and American clocks will lose some 10 minutes every hour when used in Europe. However, most modern electronic equipment like battery chargers, computers, printers, stereos, DVD players, etc. are usually not affected by the difference in cycles and adjust themselves accordingly the slower cycles.

Why can only “electric” appliances be used with a converter, and not “electronic” ones ?

The difference between a converter and a transformer lies in how the device converts voltage current. Alternating current power is supplied in alternating bursts that are in a shape called a "sine wave". To reduce 230 V to 110 V, for example, a converter chops off the sine waves in half, whereas a transformer alters the amplitude of the waves. This is a critical difference because electronic devices require a full sine wave for operation. This is why they can only operate with a transformer. Electric appliances function with either a full or a half sine wave, so they can be used with either a converter or a transformer.

The converter's "chopping" off of sine waves is a relatively simple and compact function. The transformer's alteration of sine waves is a relatively sophisticated function and requires more space. As a result, transformers are generally larger, heavier and much more expensive than converters.

Trick to know the local voltage

In case you forget to check what the local voltage is in the country you’re going to: here’s a small trick. Just take a look at the glass of an ordinary light bulb or stop at a supermarket and note what is printed on a light bulb packet !

Electrical Length - 1. Of a transmission medium, its length expressed as a multiple or submultiple of the wavelength of a periodic electromagnetic or electrical signal propagating within the medium. Note 1: The wavelength may be expressed in radians or in artificial units of angular measure, such as degrees. Note 2: In both coaxial cables and optical fibers, the velocity of propagation is approximately two-thirds that of free space. Consequently, the wavelength will be approximately two-thirds that in free space, and the electrical length, approximately 1.5 times the physical length. 2. Of a transmission medium, its physical length multiplied by the ratio of (a) the propagation time of an electrical or electromagnetic signal through the medium to (b) the propagation time of an electromagnetic wave in free space over a distance equal to the physical length of the medium in question. Note: The electrical length of a physical medium will always be greater than its physical length. For example, in coaxial cables, distributed resistances, capacitances and inductances impede the propagation of the signal. In an optical fiber, interaction of the lightwave with the materials of which the fiber is made, and fiber geometry, affect the velocity of propagation of the signal. 3. Of an antenna, the effective length of an element, usually expressed in wavelengths. Note 1: The electrical length is in general different from the physical length. Note 2: By the addition of an appropriate reactive element (capacitive or inductive), the electrical length may be made significantly shorter or longer than the physical length.

Electric Field - The effect produced by the existence of an electric charge, such as an electron, ion, or proton, in the volume of space or medium that surrounds it. Note: Each of a distribution of charges contributes to the whole field at a point on the basis of superposition. A charge placed in the volume of space or in the surrounding medium has a force exerted on it.

Electricity around the globe - There is no standard mains voltage throughout the world and also the frequency, i.e. the number of times the current changes direction per second, is not everywhere the same. Moreover, plug shapes, plug holes, plug sizes and sockets are also different in many countries. Those seemingly unimportant differences, however, have some unpleasant consequences.

Most appliances bought overseas simply cannot be connected to the wall outlets at home. There are only two ways to solve this problem: you just cut off the original plug and replace it with the one that is standard in your country, or you buy an unhandy and ugly adapter.

While it is easy to buy a plug adapter or a new "local" plug for your "foreign" appliances, in many cases this only solves half the problem, because it doesn't help with the possible voltage disparity. A 110-volt electrical appliance designed for use in North America or Japan will provide a nice fireworks display - complete with sparks and smoke - if plugged into a European socket.

It goes without saying that the lack of a single voltage, frequency and globally standardised plugs entail many extra costs for manufacturers and increase the burden on the environment.

For more information, see: Single-phase voltage and frequency, Electrical plugs and sockets

Electromagnetic Radiation (EMR) - Radiation made up of oscillating electric and magnetic fields and propagated with the speed of light. Includes gamma radiation, X-rays, ultraviolet, visible, and infrared radiation, and radar and radio waves.

Electromagnetic Spectrum - The range of frequencies of electromagnetic radiation from zero to infinity. Note: The electromagnetic spectrum was, by custom and practice, formerly divided into 26 alphabetically designated bands. This usage still prevails to some degree. However, the ITU formally recognizes 12 bands, from 30 Hz to 3000 GHz. New bands, from 3 THz to 3000 THz, are under active consideration for recognition.

Electromagnetic Wave (EMW) - A wave produced by the interaction of time-varying electric and magnetic fields.

Electronic Mail - See e-mail. - A system that allows the sending and receiving of messages through a computer. The transmission of text messages and optional file attachments over a network. Within an enterprise, users can send mail to a single recipient or broadcast it to multiple users. Mail is sent to a simulated mailbox in the network mail server or host computer until it is examined and deleted. The mail program (e-mail client) in your computer queries the mail server every so many minutes and alerts you if new mail has arrived.

Electro-Optical Intelligence (ELECTRO-OPTINT): Intelligence information other than signals intelligence derived from the optical monitoring of the electromagnetic spectrum from ultraviolet (0.01 m) through the far infrared (1000 m).

E-mail - Electronic mail - A system that allows the sending and receiving of messages through a computer. The transmission of text messages and optional file attachments over a network. Within an enterprise, users can send mail to a single recipient or broadcast it to multiple users. Mail is sent to a simulated mailbox in the network mail server or host computer until it is examined and deleted. The mail program (e-mail client) in your computer queries the mail server every so many minutes and alerts you if new mail has arrived.

E-mail Address - A computer mailing address to which electronic mail is sent.

E-mail Exploder - Synonym mail exploder, exploder. - Part of an e-mail delivery system that allows a message to be automatically and efficiently delivered to a list of addresses, thus implementing mailing lists.

Emergency Video Description - Video descriptions are a way to inform people who are blind or have other vision disabilities of what is happening on the television screen. Video description is the insertion of verbal descriptions about the setting and/or action in a program when information about these visual elements is not contained in the audio portion of the program. These descriptions supplement the regular audio track of the program.

Emission - 1. Electromagnetic energy propagated from a source by radiation or conduction. Note: The emission may be either desired or undesired and may occur anywhere in the electromagnetic spectrum. 2. Radiation produced, or the production of radiation, by a radio transmitting station. For example, the energy radiated by the local oscillator of a radio receiver would not be an emission but a radiation. 3. The electromagnetic energy radiated from an antenna.

Emission Security - Protection resulting from measures taken to deny unauthorized persons information derived from intercept and analysis of compromising emanations from crypto-equipment or an information system (IS). [INFOSEC-99] Synonym [in INFOSEC] emissions security.

Encoding - See analog encoding. The portion of the analog-to-digital conversion process that samples an analog signal and creates a digital signal that represents the value of the sample. Note: Multiple samples are needed to digitize a waveform over a time interval.

Encryption - A way of making transmitted data, such as e-mails, unreadable to everyone except the receiver. If the data is intercepted by anyone as it travels over a network, it cannot be read. Only those persons that have the right type of decoding software can unscramble the message. Encryption is used to protect e-commerce and financial transactions.

End Distortion - In start-stop teletypewriter operation, the shifting of the end of all marking pulses, except the stop pulse, from their proper positions in relation to the beginning of the next start pulse. Note 1: Shifting of the end of the stop pulse is a deviation in character time and rate rather than an end distortion. Note 2: Spacing end distortion is the termination of marking pulses before the proper time. Note 3: Marking end distortion is the continuation of marking pulses past the proper time. Note 4: The magnitude of the distortion is expressed as a percentage of an ideal pulse length.

End Exchange - Synonym end office. - A central office at which user lines and trunks are interconnected. Synonym end exchange.

End Instrument - A communication device that is connected to the terminals of a circuit.

End Office (EO) - A central office at which user lines and trunks are interconnected. Synonym end exchange.

End-of-Transmission-Block Character (ETB) - A transmission control character used to indicate the end of a transmission block of data when data are divided into such blocks for transmission purposes.

End-of-Transmission Character (EOT) - A transmission control character used to indicate the conclusion of a transmission that may have included one or more texts and any associated message headings. Note: An EOT is often used to initiate other functions, such as releasing circuits, disconnecting terminals, or placing receive terminals in a standby condition.

End-to-End Signaling - The capability changeover procedure to be used whenever the normal one cannot be accomplished (i.e., in case of some failure in the signaling terminal equipment or in case of inaccessibility between the two involved signaling points).

Enhanced 911 (E911) - Technology allowing 911 calls from cellular phones to be routed to the geographically correct emergency station (a.k.a. PSAP: Public Safety Answering Point). VoIP users currently have limited access to 911 services, and with some providers none, because VoIP is not geographically based.

Envelope - The boundary of the family of curves obtained by varying a parameter of a wave. See figure under amplitude modulation.

EO - Abbreviation for End Office - A central office at which user lines and trunks are interconnected. Synonym end exchange.

EOT - Abbreviation for end-of-transmission character.

EPG - Electronic Program Guide. An interactive list of upcoming TV programming that can be transmitted along with a DTV program

Equilibrium Mode Distribution (EMD) - That condition in a multimode fiber wherein after propagation has taken place for a certain distance, called the " equilibrium length," the relative power distribution among modes becomes statistically constant and remains so for the course of further propagation down the fiber. Note 1: In practice, the equilibrium length may vary from a fraction of a kilometer to more than a kilometer. Note 2: After the equilibrium length has been traversed, the numerical aperture of the fiber's output is independent of the numerical aperture of the optical source, i.e., beam, that drives the fiber. This is because of mode coupling and stripping, primarily by small perturbations in the fiber's geometry which result from the manufacturing and cabling processes. Note 3: In the ray-optics analogy, the equilibrium mode distribution may be loosely thought of as a condition in which the "outermost rays" in the fiber core are stripped off by such phenomena as microbends, and only the "innermost rays" continue to propagate. In a typical 50-m core multimode graded-index fiber, light propagating under equilibrium conditions occupies essentially the middle seven-tenths of the core and has a numerical aperture approximately seven-tenths that of the full numerical aperture of the fiber. This is why in-line optical attenuators based on the principle of gap loss may be ineffective or induce a lower-than-rated loss if they are inserted near the optical receiver. To be fully effective, gap-loss attenuators should be inserted near the optical transmitter, where the core is fully filled. Synonyms equilibrium mode power distribution, steady-state condition.

Erasure - [A] process intended to render magnetically stored information irretrievable by normal means.

Erlang - A unit of traffic density in a telecommunications system. One erlang is the equivalent of one call (including call attempts and holding time) in a specific channel for 3600 seconds in an hour. The 3600 seconds need not be, and generally are not, in a contiguous block. In digital telecommunications, the voice signals are compressed. This makes it possible for one channel to carry numerous calls simultaneously by means of multiplexing. In theory, there are many ways in which a channel can carry a certain number of erlangs. For example, a traffic density of 3 erlangs can consist of three simultaneous calls, each lasting for an hour (a total of 10,800 seconds); it can consist of six calls, each of which are allocated 30 minutes (1800 seconds) of time during the hour; it might consist of 180 calls, each of which occupy one minute (60 seconds) of time during an hour. Smaller units of traffic density are sometimes used. The hundred or centum call second or CCS is the equivalent of one call for 100 seconds out of an hour. A traffic density of 1 CCS is equal to 1/36 erlang. An erlang can be applied to the group of lines in a telephone trunk line or to the traffic in a telephone call center.

The term is named after the Danish telephone engineer, A. K. Erlang, the originator of queueing theory.

Error - 1. The difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value. 2. A deviation from a correct value caused by a malfunction in a system or a functional unit. Note: An example of an error is the occurrence of a wrong bit caused by an equipment malfunction.

Error Control - Any technique that will detect or correct errors.

Error Message - In a computer or communications system, a message that indicates that an error has been made and, sometimes, the nature or type of error.

Error Ratio - The ratio of the number of bits, elements, characters, or blocks incorrectly received to the total number of bits, elements, characters, or blocks sent during a specified time interval. Note: For a given communication system, the bit error ratio will be affected by both the data transmission rate and the signal power margin.

Ethernet - A network link that can transmit approximately 10,000,000 bits per second. Ethernet is the most widely-installed local area network ( LAN) technology. Specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless LANs. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD ) protocol.

Fast Ethernet or 100BASE-T provides transmission speeds up to 100 megabits per second and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second). 10-Gigabit Ethernet provides up to 10 billion bits per second.

Ethernet was named by Robert Metcalfe, one of its developers, for the passive substance called "luminiferous (light-transmitting) ether" that was once thought to pervade the universe, carrying light throughout. Ethernet was so- named to describe the way that cabling, also a passive medium, could similarly carry data everywhere throughout the network.

Evaluation - Assessment of an information technology (IT) product or system against defined security-related functional and assurance criteria, performed by a combination of testing and analytic techniques.

Even Parity - See parity, parity check. - A test that determines whether the number of ones or zeros in an array of binary digits is odd or even. Note: Odd parity is standard for synchronous transmission and even parity for asynchronous transmission.

EWSD (Electronic Worldwide Switch Digital, or, in German, Elektronisches WaehlSystem [Digital]) - A widely-installed telephonic switch system developed by Siemens. Siemens says that EWSD performs switching for over 160 million lines in more than 100 countries. EWSD is a modular system in which some switches in the system can be installed in a telephone company's centrex facility and other switches can be located at the customer.

Important features of EWSD include the following:

Line types supported include single or two-party analog, coin, TR08, and ISDN Basic Rate Interface. Unidirectional Digital Subscriber Line (DSL) support is planned. Any line type can be added by simply changing the line card.

Exchange - A geographic area established by a telephone company for specifying the local telephone service area.

Exchange Access - In telephone networks, access in which exchange services are provided for originating or terminating interexchange telecommunications within the exchange area.

Exchange Area - A geographic area served by one or more central offices within which local telephone service is furnished under regulation.

Exchange Transmission Plant - This is a combination of (a) exchange cable and wire facilities (b) exchange central office circuit equipment, including associated land and buildings and (c) information origination/termination equipment which forms a complete channel.

Expander - A device that restores the dynamic range of a compressed signal to its original dynamic range.

Exploder - Synonym mail exploder. - Part of an e-mail delivery system that allows a message to be automatically and efficiently delivered to a list of addresses, thus implementing mailing lists.

Exposure - In INFOSEC, the potential compromise associated with an attack exploiting a corresponding vulnerability.

Extension - A catch-all term that describes additional phones attached to a single line (as in a residence or small office) or a station of a Key system or PBX.

Fax Switch Products

The Stick

Business quality Single Line Automatic Call Processor. Perfect line sharing device for your small or home business. Automatically routes calls to the right device every time! Use up to three telecommunication devices plus an answering machine on one single phone line.This is our most popular fax switch. Click here to find out more.

Your Price only Delivered*

The Stick II

Two-line Voice/Fax/Modem/Data call processor. If you use two lines in your home or business, this two-line automatic phone fax switch is what you are looking for. The only two-line Automatic Call Processor that actually turns your existing inside phone wires into a mini-network. Never worry about busy signals or missed faxes when on the Internet again. Click here to find out more.
Unique Features include:
• Call In/Dial Out Long Distance Saver
(call into it from your cell phone to make cheaper long distance calls)
• Port-to-Port Communication and Data Transfer

(works like a network over your existing phone lines.)

  Your Price only Delivered*

SR Series - Selective Ringing Call Processors

The Selective Ring call processor for distinctive ringing service. Only ring the device intended for that call. Just call its phone number and it rings. Instead of having one phone number for 2 or 3 devices, you have 2 or 3 phone numbers and only pay for one phone line.

Each device has its own phone number. Works great with phone company call forwarding (forward your voice calls to your cell phone) and TDD devices too. Have a dedicated fax number, dedicated voice number and/or dedicated modem number (or a personal number) sharing your single line.

Choose from 2 or 3 distinctive ring phone numbers but pay for only one phone line plus "distinctive ring" for up to two additional numbers.
Click here to find out more about the SR-Series.

SR-2 (Two Devices - Two Phone Numbers)
Your Price only Delivered*

SR-3 (Three Devices - Two or Three Phone Numbers)
Your Price only Delivered*

Versa-Link - Industrial Grade Call Processors

Offering three models that, in addition to functionality similar to The Stick (voice/fax/modem call processor), dtmf and cng tone recognition, DIP switch programmability, phone line surge protection, remote diagnostics and an internal busy signal. Highest quality automatic call processor on the market today! Ultimate in reliability and dependability.

ATX-250 (Two Devices) In addition to tone detection, the ATX-250 Automatic Call Processor can process selective ring detection. For heavy duty applications.
Click here to find out more about the ATX-250.

Your Price only $196.00 Delivered*

ATX-300 (Three Devices) 3 device (plus an answering machine) Automatic Call Processor designed for ultimate reliability. Industry leader for almost 20 years.
Click here to find out more about the Ultra-Reliable Versa-Link.
Your Price only $299.00 Delivered*

ATX-300/6 (Six Devices) - 6 device Automatic Call Processor for multiple devices. Typically used when polling multiple modems.
Click here to find out more about the Ultra-Reliable Versa-Link.

Your Price only $479.00 Delivered*

® ACP 3,5,9


An Industrial Grade Automatic Call Processor eliminates dedicated phone lines by expanding the number of devices you can connect to a single line. Use the Polnet for modems, data and credit card terminals, storage and monitor systems, and more! This Modem Sharing Device has special polling features and interfaces with an rj-31x jack used for larger phone systems. Able to poll multiple devices (modems) in a single call. Typically used in multiple location (store) applications. Inquire about our RAD (Remote Access Dialer) for use with multiple location polling applications with this product. Click here to find out more about Polnet..

ACP-3 (Three Devices)
Your Price only $249.00 Delivered*

ACP-5 (Five Devices)
Your Price only $309.00 Delivered*

ACP-9 (Nine Devices)
Your Price only $599.00 Delivered*

Line Hunter


Rack Mounted 4/12 Automatic Distinctive Ringing Processor Processor eliminates dedicated phone lines by expanding the number of devices to twelve on up to 4 phone lines. Either have up to 12 unique phone numbers on 4 lines using your local phone companies distinctive ringing service or up to 1-4 incoming phone numbers on 1-4 lines with up to 12 outgoing devices without ordering distinctive ringing. You get up to 3 incoming phone numbers on each phone line and it hunts for an open line on outgoing calls so you never get a busy signal.

Use the Line Hunter for private phone numbers, business numbers, personal numbers, modems, data and credit card terminals, storage and monitor systems, and more!
Click here to find out more about LineHunter

Line Hunter (Up to 12 phone numbers on up to 4 phone lines)
Your Price only Delivered*

Power Controller Products

The Power Stone® - Phone controlled and secure power on/off switch for your computer.

A call-activated AC power controller. Reboot and power up/down off-site computers and other devices by phone.
Power up/down your computer from any phone in the world.
Click here to find out more about The Power Stone.

Your Price only $129.00 Delivered*

The Internet Power Stone® - Internet controlled and secure power on/off switch for your computer.

The IPS provides various methods of initiating an AC power reset to meet any requirement for complete in and out-of-band network control. By Telephone: The basic reboot function involves an incoming POTS line and a connected AC device.  By Heartbeat: The IPS can work with heartbeat software that will automatically reboot a computer when a problem occurs. By Web-browser: The IPS can be controlled by a master control unit that is accessible via the internet.
Click here to find out more about The Internet Power Stone.

Your Price only $199.00 Delivered*

The Internet Control Module® - Internet Controller for Internet Power Stone (above).

The ICM is a web based network manager used to control any of Multi-Link’s power control base units.The ICM connects to a web-based network like any other IP network device and acts like a mini-website, accessible via any web browser.  Base units for reset or AC power control can be located as far as 2,000ft away from the ICM network power manager.
Click here to find out more about Internet Control Module.

Your Price only $259.00 Delivered*

*Note: All prices include shipping and handling in the continental US and most of Canada. We reserve the right to charge up to the actual price of shipping on all orders outside the continental United States. Customer is responsible for any taxes, duties or brokerage charges that may apply. All orders shipped UPS Ground unless specified. For air and express shipments, appropriate charges will be applied to your order.

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Need Help? - Call now for free phone consultation at 1-866-337-0965.

Click here if you want to share 2 devices on 1 line and don't know which device to choose.

Click here if you want to share 3 or more devices on one line and don't know what type to choose.

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