Bell
Technical Support
System
Tel 0845 121 4008
(Telephones) Ltd
Fax 0845 121 4009
Web
www.bellsystem.co.uk
Low volume speech in
one or both directions
1. Adjust pot on 51/61 speech unit marked A (with a
speaker symbol) for volume at the panel.
2. Adjust pot on 51/61 speech unit marked B (with a
microphone symbol) for volume at the phone.
3. If volume cannot be increased in one direction
without feedback, the volume in the other
direction may have to be reduced as a
compromise.
4. Check model 51/61 is hard against the panel with
no gaps.
5. Check model 51/61 speech unit is the right way
round
6. If using a 61 speech unit check the microphone
single hole lines up with the hole in the panel.
7. Another phone (801, 801S and phones without
privacy of speech) is off-hook. To check either go
round each phone or:
Power the system down, disconnect cores O and
T from the speech unit and measure the
resistance between those 2 cores. A high
resistance (KOhms) means all are on hook. A
resistance of Approx. 60R or less indicates a
phone off-hook, or a partial cable short for 1
direction of speech.
1 Way speech / No
speech from phone to
entrance
1. Missing or shorted ‘R’ connection
1 Way speech / No
speech from entrance to
phone
1. Missing or shorted ‘T’ connection
Low frequency hum
heard (50Hz)
NOTE: There will always
be a faint hiss/hum at the
speech unit, but you
should have to put your
ear up to it to hear it.
1. Cores R and O are not in the same pair.
2. Twisted-pair cable has not been used.
3. There is a mains cable running next to the door
entry cable.
