Testing for break in wires

[wayne73]

I am just about to investigate why several handsets have different types of connections issues to an audio door entry system. Some buzzers do not work, some can hear but not speak and some have a working door release and some do not. A bit of a mess. Now before i replace the main control unit and handsets i would like to simply test each wire to ensure there are no breaks. I was thinking about using a multimeter on each wire at either end and ask smeonme to press buttons and talk and then measure activity on each wire.

Thanks and thoughts.

 

[Taylortwocities]

A continuity test using a multimeter, without any of the current equipment attached would be a start.
It does sound like a central problem if several flats have the same problem.

 

[wayne73]

thx for the advice...serveral flats do have the same problem and serveral flats have others issues, thats why i am thinking some of wires have been damaged somewhere through the building or the handsets are developing random technical issues my guess is the wires.

 

[ColJack]

if it's several flats with differing problems, then the fault is likely the unit at the door.. where all the wiring will converge, unless it's a system with a central control panel then it's probably that..

it'll be odd to find that several sets of wiring going to different places are all damaged, unless it's where they get bunched together at on point..

 

[bernardgreen]

If different handsets have different problems I would first suspect the handsets. If it was a fault in common equipment ( cable or controller ) most handsets would have the same faults.

Some of these door entry systems are very simple and run a multi-wire cable to all handsets ( or to a junction box nearby )

Speech pairs are common to all handsets, If two or more handsets are picked up at the same time then they can all talk to and from the door and to each other.

Door release buttons are commoned onto one wire,

Only the bell wires are unique to each handset.

A short on a speech pair far ( in cable terms ) from the front door will knock out that speech on adjacent handsets but handsets closer to the door may still work but at very reduced volume.

At each handset or a nearby junction box there will be the cable with many wires not connected, these are bell wires for other handsets.

There is one system for up to 100 flats ( seldom seen ) where pressing a door bell ( two pole button ) puts positive on one wire of 10 and negative on one wire of another 10. Buzzers in handsets have a diode and each is connected to one of the negatives and one of the postives. So 20 wires can operate 100 buzzers leaving 5 ( in standard 25 core cable ) for speech and door release.

 

[wayne73]

Thanks again, the reason why i want to test the cables is because i am not going to mess around trying to fix individual handsets, i will test the integrity of the cables and then replace all equipment (10 handsets, 1 audio entry system) if the cables are fine.

 

[delmel]

My guess is nothing wrong with the cable itself. Two common problems

wrong cable used (volt drops big issue)

main problems person installing has done so incorrectly.

If not a regular installer look at the two wire systems.