PETS-2 Crossing Telephone System
QUICKFIX INSTALLATION HANDBOOK
Page 3
of 40
Issue 2
13/12/99
3
remote location. Within the Junction Box, Block 3 is dedicated to these isolated circuits. The
25 way ‘D’ connector and its 10 pair cable are also dedicated to these isolated circuits. DO
NOT make connections between Block 3 circuits and other circuits of the PETS 2 system.
The Telecommunications safety earth is relevant to the local PETS 2 Telecommunication
circuits (Crossing Telephones), the PETS 2 power supplies and electronics. The ‘isolated’
circuits to remote sites via physical circuits or transmission equipment are always isolated
from the local earth (this is to ensure that ground potential differences do not cause
circulating currents)
WIRING
Telephone circuits carry low level signals, of a few hundred milli-volts. These
circuits are particularly susceptible to external electro-magnetic influences. It
is always advisable to avoid routing these cables near to power cables or
other potential interference sources. Provision is made within the Junction
Box for earthing of the cables, do so at the Junction Box end only. Ensure
there is a low impedance path to earth from the Telecommunications Earth
within the Junction Box.
LIGHTNING
A risk of lightning damage exists if the cables are external to a building, and/or the physical
circuit is overhead. If the risk of lightning strike is low then QDF protection
magazines should be fitted within the Junction Box, on the circuits at risk. If
the risk is high (cables conveyed overhead, or track-side) then separate
lightning protection should be installed, using a separate protection unit and
a dedicated earth point.
STATIC SENSITIVE PRECAUTIONS
PETS 2 plug in modules use components that are static sensitive. When
removing/ fitting plug in cards ensure that an anti-static wrist strap is worn.
The strap should be connected to the earth stud provided and marked with
the ‘Static Sensitive Handling’ label.
