The simplest of Simple Telephones is the familiar home telephone
consisting of handset and base, which can make and receive
calls, but little else. For many people this is all they need.
Such devices are readily available costing upwards of a few
There have always been more exotic devices, using the same
technology, to perform specific functions and jobs. With deregulation
of the telecommunications market the number of such devices
available and the jobs they do has increased and will continue
to do so, becoming a part of our everyday lives.
This chapter introduces the most common types, giving an description
of a typical device, outlining the type of features that will
be encountered and commenting on the benefits and drawbacks
of each type.
The Telephone Answering Machine (TAM) together with the cordless
telephone are probably the most widely known developments
of the simple telephone device, being found today in most
homes and offices.
The TAM in its basic form is a call receiver which will, in
the absence of the owner, answer a call, play a greeting message
and invite the caller to leave a message, which is recorded
for playback when the owner returns.
There is no requirement for outgoing calls so there is no
handset or dial functionality included. The unit is connected
across the line in parallel with the standard telephone. With
correct installation the TAM function can be interrupted by
picking up the parallel handset to take a call in the process
of being answered.
Figure 5 shows two methods of connection between telephones
and answering machines. The first is a parallel connection
between the two and the second shows the TAM fitted between
the telephone and incoming line. Some TAM equipment has a
socket provided for this type of connection.
Figure 6 - Connection Of Telephone
So far the basic TAM has been described. It is now common
for the TAM function to be included as part of the functionality
of a more complex telephone or facsimile machine. These are
referred to as TELTAM and FAXTAM. There are also enhanced
TAMs which offer more than simple message recording.
More recent features found on TAMs include:
Time / Date Stamping A synthesised voice records the
time and date after each message.
New Message Play Only the new, unheard, messages are
played back. Older messages being stored for later review
Remote Access The owner can dial into the machine from
an external telephone and recover messages and/or modify the
Announce Mode The TAM plays a recorded message to callers,
but does not accept or record a message from the caller.
External Delivery Found on very few TAMs. An external
number is dialled and the messages recorded are played back,
usually after entry of a user PIN Number.
Digital Recording Messages are stored in electronic
memory instead of tape. These machines are more expensive,
but do not wear out as quickly as tape based TAMs.