Bell System 9nn Series User manual

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
Web www.bellsystem.co.uk
Troubleshooting Guide
Audio Door Entry Systems (single entrance)
9nn, VRKn or BLn series)
Most systems use the 801 phone, 801P on systems above 20 flats.
Twisted-pair cable must be used CW1308 telephone or Cat5e data cable). Alarm
cable is not recommended and can cause problems with speech.
Phone connections
Terminal
Meaning
I Call / call button 12V to ring)
R Microphone
O Common for ring, speech and lock button 0V)
T Speaker
Z Lock button Z shorts to O when the lock button is pressed)
V 12V DC Phone supply BS-LX and 500X series only)
L Door Monitor connecting L to 0V brings green LED on, BS-LX and
500L series only)
51 Speech unit – 12V AC or DC operation
61 Speech unit – 12V AC or DC operation
801 Series phone with Electronic ring – 12V AC or DC operation
801 Series phone with Mechanical buzzer – 12V AC only
500A, PA – 12V AC only, other 500 series 12V DC only
If a phone has 500 PAD on it check which letters are crossed out. If the A is crossed
out the model is a 500PD.
BS-LX phone – 12V DC only
ommon Faults
A very high percentage of calls to our technical support number, regarding new
installations, are resolved to faulty wiring. The reasons for these are various: -
• Broken cores, especially short links, sometimes broken inside the insulation.
• Connectors clamped onto the insulation instead of copper.
• Short or open circuits due to cables having been stapled or nailed through.

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
Web www.bellsystem.co.uk
• A common fault is wiring a connector left to right instead of right to left, or one or
more twisted pairs the wrong way round.
Tip. The heads of screws on connectors are not a reliable means of making a
connection with a meter, try pushing the probe into the wire entry point.
The following tables provide a quick indication of the possible fault:
Lock Release Problems
Lock release does not
operate.
1. Connections to the Lock release are
open/short-circuited note power supply fuse
may have blown).
2. Poor connection or damaged wire in the lock
release circuit. Check cable to lock release
and cable to Z / O terminals on the phone.
3. Voltage drop issue; cable diameter is too
small, try doubling up on the lock button
cores Z & O going to the phone s).
4. Dodgy lock release button on the phone.
Simulate a lock button press by shorting Z &
O to prove.
5. Lock release current is too high if using a
third party lock release). An additional relay
and suitable power supply maybe required.
Check the lock release current plus 0.5A for
the system does not exceed the power supply
rating.
6. Lock release jammed due to over tight fitting;
check there is some ‘play’ between the lock
and lock release. Do not fit the tongue on the
door to deep.
7. Faulty lock release. Connect Z side of lock
release to H on the speech unit to force 12V
across it and test.

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
Web www.bellsystem.co.uk
Lock release buzzes, but
doesn’t unlock
1. Poor connection or damaged wire in the lock
release circuit. Check cable to lock release
and cable to Z / O terminals on the phone.
2. Voltage drop issue; cable diameter is too
small, try doubling up on the lock button
cores Z & O going to the phone s).
3. Dodgy lock release button on the phone.
Simulate a lock button press by shorting Z &
O to prove.
4. Lock release current is too high if using a
third party lock release). An additional relay
and suitable power supply maybe required.
Check the lock release current plus 0.5A for
the system does not exceed the power supply
rating.
5. Lock release jammed due to over tight fitting;
check there is some ‘play’ between the lock
and lock release. Do not fit the tongue on the
door to deep.
Lock release operates all the
time.
WARNING: Not all lock
releases are continuously
rated; this may cause it to
burn out.
1. Short on the lock button cable core going to Z
on the phones. Probably to power supply
common Terminal H or O).
2. Lock release button stuck in or faulty.
Disconnect Z terminal from the phone in
question and see if the fault disappears.
Trades button doesn’t work
where fitted)
1. No power to the Time Clock, check the time
clock can be forced on.
2. Time clock settings not working, force the
time clock on to check. Note the TS2000 -
BST) time clocks need to see the time
change to operate.
3. Time clock not working. Short the CO and
N/O terminals together to bypass.
4. Break in the trades button circuit.

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
Web www.bellsystem.co.uk
Telephone Ring Problems
Phone doesn’t ring 1. Broken wire between the call button for that flat
and the phone Terminal I). Try a spare core.
2. Broken wire between the phone Terminal O) and
the speech unit. Check if the lock button or
speech work, if either does then the O connection
is ok.
3. No voltage getting through to I and O terminals
on the phone. Check at least 10V across I and O
when the call button is pressed or shorted.
4. Dodgy call button. Short the 2 terminals to prove.
5. Missing connection between C on the speech unit
and the call buttons no phones ring).
Phone ring’s but not
heard at the entrance
1. Missing ‘R’ or shorted connection between phone
and speech unit. There will also be no speech
heard at the entrance.
BS-LX phone flashes red
and green periodically
instead of ringing
1. No 12V DC to connection ‘V’, check at least 8V
between V and O on the phone when it is ringing
highest current). Also check there is power at the
phone by pressing the bell button on the phone
and seeing the mute light come on.
Mute LED won’t light on
a phone.
not all models)
1. No 12V DC on terminal ‘V’.
Door open LED does not
come on, on the phone
not all models)
1. No 12V DC on terminal ‘V’
2. ‘L’ terminal no shorting to 0V when the door is
open. Connect L to O on the phone to check
phone.

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
Web www.bellsystem.co.uk
Speech Problems
Acoustic feedback:
Loud tone/howl at the
entrance speaker and
phone, whenever the
handset is taken off
hook. Sometimes this
effect is continuous and
sometimes it will vary
with the position of the
handset or appear only
whilst talking.
1. Either or both volume controls are adjusted too
high. Normally both A and B should be adjusted
to between one third and one half of full rotation
to achieve good speech volume without
feedback.
2. The >O= connection is not properly made. Mis-
connection of the O-line between the speech unit
and the telephone will dramatically reduce the
feedback threshold. Check your wiring for this
fault. If the phone rings or the lock button works
this cause is unlikely they also use the O).
3. There is an air gap between the speech unit and
the grill. The speech unit must be placed firmly
against the rear of the grill of the entrance panel;
if necessary use packing materials to achieve
this.
4. The Entrance Panel and Telephone are located
too closely together. If the caller can be heard
directly i.e. without the use of the entry phone
system) then the units are too close!
5. The environment is too noisy. If the entrance
panel is placed in a noisy environment such as
on a busy high street, it may be difficult to obtain
satisfactory volume levels. Try sacrificing the
volume in one direction to the benefit of the other.
6. The entrance panel is placed in an >acoustic well=.
If the entrance panel is surrounded by reflecting
walls e.g. a basement flat then acoustic feedback
may occur at lower volume levels. Try changing
the position or orientation of the panel.
7. Twisted-pair cable has not been used. The
maximum volume achievable can be reduced
with other types of cable, especially when the
amount of cable or length of runs become
significant.

Bell Technical Support
System Tel [phone]
(Telephones) Ltd Fax [phone]
Email [e-mail]
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.