Wirral & District Amateur Radio Club

Telecoms & Accessories



With the trend towards working from home, there is an increase in communication equipment in the home such as telephones, fax machines, computers and modems to access the internet. Multi-function machines are now available which offer fax, copier, printer, PC-fax, scanner and e-mail from one unit.

Internet, Modem and Interactive Services

A modem is a device which allows a computer or Digital Set Top Box (STB) to send and receive information over a telephone line. It can be an internal device built into the desktop, laptop, or STB, a separate external box that connects to a computerís serial port, or a PC card that plugs into the PC card slot found on most laptops.


There are basically four types of telephone:

1. Analogue Corded The traditional telephone with a fixed cord from the phone base to the handset.

2. Analogue Cordless The first system of cordless technology with limited operating distances.

3. New Frequency Analogue Cordless

An enhanced system which uses eight channel technology, a new frequency range of 31-39MHz and gives clearer call and larger operating distance approx. 100m away from the base station.

4. DECT-Digital Enhanced Cordless Telephony
DECT phones that use digital cordless technology operate on 1.8GHz and allow multiple handsets to be used from a single base station, offering significantly greater range than analogue models, improved reception and clearer speech.

Combined mobile/DECT cordless phones provide mobile and DECT features in one smart handset, which can accept or make calls on both mobile and land line networks. These use DECT protocol close to the home and automatically switch to mobile use outside a certain range.

Fax Machines

Fax machines plug into a telephone socket and have built-in software to enable the user to transmit data for instance, a letter, which can be received normally by another fax machine. Early fax machines used thermal paper but more modern machines print directly onto standard A4 paper.


Modems are available in a variety of speeds. The faster the modem, the quicker the data can be transferred and hence the shorter and cheaper the phone call will be. This is provided the telephone line and other end of the line can support the modem speed and protocol.

To connect a modem to a telephone line, the socket will need to be a BT style socket. See following section on BT style sockets and installing extensions. Faster access speeds are possible using ISDN digital phone lines, or services such as BT Highway which adds a digital line alongside your existing phone line. To connect your computer to the digital line you need an ISDN adapter rather than a modem, and the Internet Service Provider you choose must offer ISDN support.

An alternative to the PC-modem-phone line or PC-ISDN approach is to connect through the mobile phone networks, either by linking a laptop to a mobile phone through a data card or an infra-red link. Cable modems and STB modems are often used as the return path for the interactive services offered by the terrestrial, satellite or cable operators. These modems may also offer internet access via the STB.

Telephone Extensions

Before installing a telephone extension, it is important to note the Ring Equivalent Number (REN). Telephone lines have a REN of 4- they can operate up to 4 telephone accessories (e.g. phones, fax, answerphone), each with a REN of 1.

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Reproduced here by kind permission of Click for Maplin website

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