Codan NGT 2010 RF Technical & Service Manual page 796

1
Checking the transceiver
If the interface cable is not at fault, then the transceiver should be checked (see
NGT—Technical description
No reception, without signalling
NOTE
If there is no reception and commands are not functioning from the transceiver (such as
channel changing) then the fault may be in an area shared by the receive and signal path.
Alternatively, this may be the result of two separate faults: no receive, and no signalling.
If a signalling fault still exists after repairing the receive fault, continue to check for a
signalling fault (see
To assist in locating a receive fault, check the 2-wire or 4-wire link, the master 8571, the
slave 8571, and the transceiver as follows.
Checking the line
To check the line:
1
1
1
1
NGT Transceiver System Technical Service Manual
From here the remaining receive path is shared with the signalling path and
therefore is unlikely to be faulty.
If the signal is absent at any of the test points, examining the neighbouring circuits
should assist in locating the fault.
The following fault finding procedure is based on a remote control system
consisting of a single master 8571, a single slave 8571, and a transceiver.
In the case of multiple systems, consideration must be given to the other
units within the network when tracing this type of fault.
page 354, No
Check the 2-wire or 4-wire link using an audio amplifier with a speaker or an
oscilloscope for receive noise.
If there is no receive noise on the line and the 8571 proves to be operational, check
the line by applying a known level of 1 kHz tone (say 0 dBm) from a 600 Ω source
at one end, then measure the level at the other end when terminated into 600 Ω.
Check the attenuation meets specification.
Check both directions for a 4-wire system.
(2010)).
signalling).
8571—Fault finding
page 69,
357