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18
CHAPTER TWO
Using Extension Telephones
It may be that your premises are already wired with parallel extension
telephones, or you intend to add extension telephones to your line, in
addition to your machine. While the simplest arrangement is
straightforward parallel connection, there are some reasons as to why this
arrangement will cause unsatisfactory service, the most obvious of which
is inadvertent interruption of a facsimile transmission by someone
picking up an extension telephone in order to make an outgoing call.
Additionally, remote activation may not operate reliably in such a simple
configuration.
This machine may also be set to make a delayed transmission (i.e. a
transmission at a pre-set time). This pre-set job may coincide with
someone picking up an extension handset.
Such problems can easily be eliminated however, if you arrange
modification of your extension wiring circuit, such that extension devices
are connected “downstream” of your machine, in a master/slave
configuration. In such a configuration, this machine can always detect
whether a telephone is in use, thus it will not attempt to seize the line
during that time. This is known as “telephone off-hook detection.”
The inadvisable configuration is shown in figure 1 below, and the
recommended master/slave configuration is shown in figure 2.
This new connection configuration can be arranged by your contacting
BT, Kingston upon Hull Telecommunications, your PABX maintainer or
a qualified telephone installation company as appropriate. Simply
explained, the extension telephone circuit should be terminated on a
normal modular plug (BT 431A style), which in turn should be inserted
into the modular socket of the white “T”-shaped connector provided as
part of the line cord assembly.
FAX
EXTENSION
SOCKET
EXTENSION
SOCKET
MASTER
SOCKET
INCOMING
LINE
INADVISABLE CONNECTION OF EXTENSION SOCKETS
Fig. 1.
EXTENSION
SOCKET
EXTENSION
SOCKET
MASTER
SOCKET
INCOMING
LINE
RECOMMENDED CONNECTION OF EXTENSION SOCKETS
Fig. 2.
FAX
FAX MACHINE MUST BE PLUGGED
INTO MASTER SOCKET
DISCONNECT