General Information on Track Circuits - RGS Online

Railway Group Approved Code of Practice
GK/RC0752
Issue Two
Date December 1998
Page F4 of 5
5 Track Circuit Fault
Detector
Withdrawn Document
Uncontrolled When Printed
<strong>General</strong> <strong>Information</strong> on Track Circuits
The clip assembly should then be plainly marked for attention by the Permanent
Way Engineer.
The brush carriers can be raised/lowered to cater for flat or Pandrol type rail
clips by moving the brush carrier handle to its vertical position to release the
locking mechanism.
Care must be taken to ensure that the rollers of the unit do not straddle any
IRJs, causing “flicking” of adjacent track circuits.
Short circuits between the rails can be difficult to locate, since, except for audio
frequency types, the short circuit results in an identical drop in rail voltage along
the length of the track circuit and gives no clue as to its physical location.
Without the Track Circuit Fault Detector, it would often be necessary to sub–
divide the trackwork to locate the faulty section.
The detector is designed to be used on the trackwork of a track circuit where the
feed and relay have been disconnected. It consists of two portable battery
powered units: a transmitter and a receiver.
Transmitter This is housed in a box incorporating an “on/off” switch and an LED
indication. Yellow leads with clips are provided to connect the unit
across the rails or lineside apparatus housing links. It is battery
powered and outputs an intermittent high frequency voltage.
Receiver This is housed in a box incorporating an “on/off” switch and an LED
indication. It is battery powered and incorporates an internal aerial,
amplifier and loudspeaker. When the receiver detects a signal
from the transmitter it outputs an audible tone.
Before commencing to test the bonding of a track circuit, the track circuit fault
detector should be checked as follows:
a) The transmitter leads should be connected together and the transmitter
switched on.
b) The receiver should then be switched on and held near the transmitter leads;
an audible tone should be heard emitting from the receiver (this simple test
will prove that the fault detector is working correctly).
c) The feed and relay ends of the track circuit under test should be
disconnected. With jointless track circuits, the track circuits either side of the
track circuit under test should also be shorted out.
d) The transmitter should then be connected across the rails at the feed end
and switched on. The receiver is switched on and held near the rail; an
audible tone should be heard emitting from the receiver. No tone may
indicate a bad connection to the rails. If the rail connections are good, the
fault is an open circuit, which may be found in the conventional manner. If an
audible tone is heard, the receiver should then be carried along the track
near to the rail and when the receiver passes the short circuit, a distinct drop
in the volume of the tone will be noted.
F4 R A I L T R A C K