Door entry

Voice intercom and remote sounder system

A typical block entry system for flats. It has four functions :

• Entrance door button to sound a buzzer in one individual flat
• Entrance door-lock release. A common line so the lock can be opened from any flat
• Speech from a microphone in the entrance panel that can be heard in any handset speaker
• Speech from any handset microphone heard from a speaker in the entrance panel.

1980's-era typical system description

The enrty-phone is a white plastic wall-hung handset like a telephone. Lifting the handset releases an off-hook switch which makes the microphone and speaker live and you can then talk to anyone outside. You can also speak to anyone else with an off-hook handset. There may be an amplifier in the system or it may be just a signal voltage generated by a carbon microphone and heard in a sensitive speaker. All that would need to work is a small direct current (DC) voltage to energise the microphone.

The buzzer and lock circuit is separate and runs on alternating current (AC) low voltage and it's the 50Hertz buzz you can hear at both.

Often the entry panel has back-lighting for the call buttons, this is also run from low-voltage AC.

The handset is hard-wired through a multicore telephone-type cable having 5-6-8 strands, usually in colour coded pairs e.g. blue/white + white/blue, same for orange, green, brown. Looking at a compatability chart on a supplier's website, there is no common use of numbering or colouring between manufacturers.

Circuit diagrams

In general, five wires go to the handset from the entry panel. Call - Talk - Common - Hear - Unlock. The CALL wire will only show a voltage when the entry button is pressed and will appear across the buzzer terminals. The other side of the buzzer is the common terminal. The door-open button on the handset also connects to the common one and pressing this will drop the voltage on the UNLOCK terminal and so identify itself. Knowing those three terminals, the other two are Talk and Receive. and the R will make a scratching in the speaker if you disconnect and reconnect its wire. That should give you the connections.

... to be continued. Any info gratefully received!

Trouble-shooting

Try this link

https://doorentrydirect.com/acrobat/bell/data/Bell%20801%20Trouble%20shooting.pdf