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I live in a condominium. There is a door intercom system (see picture 1). The intercom is made by BPT company (Italy), model E/272 (see diagram in picture 2).

Since there is too much noise, I can't hear the buzzer when somebody from outside is pressing the button to notify me to open the door. I want to install a second buzzer or ringing bell in my computer room.

Although I have the instructions (see picture 3) I don’t know which terminals to connect in order to run a cable to connect a relay to operate the new buzzer. I don’t even know which is the buzzer and which is the microphone. Please advise me which terminals should I use.

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ocrdu
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NickRucunas
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  • Dear Peter Good day I tested the contacts 5 & 7 with a multimeter set to 0-200V AC while a friend pressed the button. the indication was 6.7 Volts. You was absolutely right. Now if I am not overuse your time please kindly make a sketch (not electric diagram) how should I run the cables and the connections to devices. Thank you very much again. NickRucunas P.S. By the way the intercom is a replacement of one of the same company which was installed 50 years ago and i replaced it 5 years ago using the existing cables. – NickRucunas Apr 08 '23 at 08:25

1 Answers1

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Any idea what age the circuit is? It looks like 1970s to me. Our intercom is of a similar vintage and is quite crude - the microphone is a carbon one.

Form your rather grainy photo, I'd say the buzzer is maybe the thing that looks like a relay in the top center. It has two wires coming out of it. One goes to the green terminal block and the other goes to the white terminal block. They're supposed to be terminals "5" and "7". I'd put a voltmeter across those two terminals and get a friend to press the downstairs button. The buzzer is probably AC so you'll need to set the meter accordingly.

Is the buzzer 6V or 12V? It depends on the model number.

If it's AC, you'll need a rectifier in order to operate you extension buzzer. I wouldn't use a relay, I'd just use a modern electronic sounder. They take a very small current compared with the ancient buzzer in your intercom. Look on eBay for "sounder 6V" or "sounder 12V". The first hits I got are:

https://www.ebay.co.uk/itm/372371793332 https://www.ebay.co.uk/itm/125387551594

Also search for a "bridge rectifier", e.g.

https://www.ebay.co.uk/itm/285022072920

(you may want to limit the search to your own country so as to get quicker delivery.)

And a smoothing capacitor - e.g. 470uF 25V

https://www.ebay.co.uk/itm/202799914226

Do you need help with the circuit diagram?

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Here it is. Note that each component should be marked with "+" and "-".

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Peter Balch
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  • Thank you very much Peter for your help and the prompt answer. I will try tomorow, and I will let you know. Have a nice afternoon. NickRucunas. – NickRucunas Apr 07 '23 at 18:05
  • Dear Peter Good day I tested the contacts 5 & 7 with a multimeter set to 0-200V AC while a friend pressed the button. the indication was 6.7 Volts. You was absolutely right. Now if I am not overuse your time please kindly make a sketch (not electric diagram) how should I run the cables and the connections to devices. Thank you very much again. NickRucunas P.S. By the way the intercom is a replacement of one of the same company which was installed 50 years ago and i replaced it 5 years ago using the existing cables. – NickRucunas Apr 08 '23 at 08:26
  • I've edited my answer. Any capacitor over maybe 270uF should be OK. The working voltage should be more than twice your expected voltage, e.g. 16V or 25V. The sounder should be the kind that, if you give it a voltage then it will make a noise. That means the eBay page will say a frequency somewhere, e.g. 2000Hz. Any bridge rectifier you can find on eBay will work - get the cheapest. Maybe you have a local electronics shop. – Peter Balch Apr 09 '23 at 10:19
  • If you're not happy soldering, you could make the circuit by poking the components into a screw terminal block. – Peter Balch Apr 09 '23 at 10:28
  • Two questions: 1) Does the cables length (e.g. 5 meters) play any role? 2) Buzzer should be AC or DC? Have a nice Sunday evening!! – NickRucunas Apr 09 '23 at 17:35
  • Cable length shouldn't matter - the current is small. The sounder is DC. Connect the bridge rectifier and the capacitor and measure the voltage across the capacitor. It should be between 6V and 12V - my guess is about 9V. You want a sounder which will work at that voltage. A 6V sounder might be damaged by 9V (it probably won't) and 12V sounder might not work. – Peter Balch Apr 10 '23 at 13:55
  • I WANT TO OFFER MY THANKS TO PETER BALCH!!!!!!!!!!! As soon as I get it ready I inform you. Have a nice time. – NickRucunas Apr 13 '23 at 07:01