4.
Earth
Recall
If the system is connected to a
PBX
with earth loop recall, a signalling earth must
be connected to the
CCU.
The earth should be connected to either of the terminals marked
'E' on the exchange line terminal block. The earth is fed to each extension telephone from
any of the terminals on the "Recall Earth" block and the second 'E' terminal on the
exchange line block.
Note:
with six extensions it will be necessary to connect two
extensions to the same earth terminal.
CABLING DISTANCES
To ensure satisfactory operation of the system:
a.
the maximum loop resistance for an extension with earth loop
recall is 60JJ.... This is equal to a 355 metre run of 0.5 mm copper
cable;
b.
the maximum loop resistance for extensions where recall is not
provided is 100D..,equivalent to a 595 metre run of 0.5mm copper
cable;
c.
if the conference facility is not to be used the maximum loop resistance
for extensions may be increased to 500Q1equal to 2975 metres of 0.5 mm
copper cable.