How do I silence the telephone ring from my doorbell intercom ?

[robolo]

I have a front door intercom system that connects to my phone system. When someone pushes the "doorbell" on the unit it establishes a telephone connection to the house phones, causes a distinctive ring and then any telephone can be picked up to talk to the visitor.

What I would like to do is use my ELK to play "ding-dong" over the speakers and NOT have the phone ring but still have the phone connection available to talk with the person at the door.

I can do the ELK part but essentially I want to eliminate the voltage spike from the doorphone unit that would normally cause the phones to ring but not affect the front-door line connection when the telephone is taken off-hook. The manufacturer wouldn't discuss with me how to do that. Any ideas?

 

[gatchel]

Install a doorbell button to a zone input and disable the button on the intercom. By disable I mean cut a circuit trace or physically disconnect the door intercom button internally.

What telephone intercom system is it?

Maybe there is a way to get a dry contact off of the intercom unit or the intercom interface box.

Johny 5 needs more input...

 

[robolo]

gatchel, thanks for the reply. The connection to the ELK is no problem. No assist needed there.

I cannot disable the doorbell button because it initiates the sequence of creating the phone circuit from the front door to the phone system.

The maker is Quantometrix and the product is the PhoneBell Q-10s. It has a ring generator that produces 7 REN. I need someone to tell me how to knock out the generated AC current that the ring generator produces with electrical components. Like, would I place a rectifier/diode/etc between the device and the phone system wires? With all the electronic tinkerers on this site I thought it would be an easy answer.

Another way to ask this question is...forget all about the door intercom system for a moment. What would someone need to do to cancel out the voltage spike the telephone company produces to cause the phone to ring? Lets say I want to have my telephone to call out I just never want to hear it ring. Other than turning off the ringer on the phone itself I want to wire in some components that would prevent the phone ringer voltage from passing down the phone line to the telephone but not block the phone connection voltage. There has to be a way to do that.

 

[ceady]

According to http://www.tech-faq.com/telephone-tone-frequencies.shtml
"Audible Ring Tone is 440 Hz and 480 Hz for 2 seconds on and 4 seconds off at -13 dBm0/frequency."

So if you throw a notch filter around the 460 Hz mark on the phone line coming from the intercom before your regular phone network that might get rid of the ring and still allow you to use your phone for front door calls.

Something like a Twin-T Notch Filter might work and it is an easy design and passive, so at least you can see if it works on the cheap. Check out http://mysite.du.edu/~etuttle/electron/elect15.htm part way down the page for the design.

Craig

 

[robolo]

Craig,
Thanks for assisting. The audible ring tone is produced by the telephone itself in response to the ring signal voltage. According to AT&T the ringing signal is an 88v 20Hz AC signal superimposed on 48v nominal DC supervisory voltage. The frequency of the AC signal is normally between 15 and 70 Hz.

It is this AC signal I am looking to supress. I think your suggestion has to do with the sound produced by the phone itself rather than the triggering signal. Or did I misunderstand?
Robert

 

[paulw11]

Hi,

Many of these intercoms have a sequence you can dial from the phone to connect to the intercom instead of the phone line (** or similar). Could you reconnect the intercom button to the Elk so you could trigger your doorbell sound and then pickup a phone and dial this code (assuming your system has such a code)?

Paul

 

[ceady]

Actually I was suggesting that you use a notch filter to suppress the ring signal that is sent from the Q-10 to the standard phone lines. In this manner your standard phones never receive the signal to ring. If a 20Hz signal is used then a notch filter at that frequency should stop your phones from ringing.

Hopefully that makes more sense.

Craig

 

[robolo]

Paul,
No code available to dial in on this model.

Craig,
That does make sense now and is the info I needed. I will go with that suggestion and see how it works. Thanks

Robert