Making a telephone ringer

[Ynot]

You DON'T want the phone to stop ringing when the handset is lifted, since if the talent does not replace the handset correctly afterwards and the phone has to ring again you are in trouble. It's happened to me more than once. You generate the ring pattern manually and just watch for the handset to be lifted.

Don't quite see what you're saying here...

Few phones (if any) will ring at all with the handset off hook, so how do you get it to do so if they DON'T replace the h/s properly?

And to be honest it makes little difference whether you send the ring cadence automatically or manually - the phone will either ring or it won't...

[Richard Bunting]

Just to chuck in my 2p worth. We've had to build a series of SM desks recently which required an integral phone ring generator, and found this company www.precisiovision.freeuk.com. Although not cheap, it is a very solid product which will supoort two phones if needed. It is normally supplied in a freestanding case.

 

HTH

 

Richard

[Andrew C]

All you need is a 50V 50W transformer and a push button and ideally a 1A fuse.

And it sounds rubbish! Sorry, but the whole point is that we all KNOW exactly the cadence that the thing should ring at, so when the SM gets it wrong, it jars, badly.

[daifuse]

Many moons ago, I made a ringer by using a geared down mains voltage motor (from a defunct mirror ball rotator). I made a cam with the necessary pattern of the ring timing which I attached to the shaft and this cam operated a pair of old GPO relay contacts which were connected to a 240v/50v transformer. A hefty diode (IN5004) in series with the 50v was connected to the phone cct. A simple on/off switch on the supply to the whole thing was operated as required. To obtain any cadence, just change the cam ....

It will drive old or modern phones and has been in use now for over 20 years - never a failure!

[Ynot]

Many moons ago, I made a ringer by using a geared down mains voltage motor (from a defunct mirror ball rotator). I made a cam with the necessary pattern of the ring timing which I attached to the shaft and this cam operated a pair of old GPO relay contacts which were connected to a 240v/50v transformer. A hefty diode (IN5004) in series with the 50v was connected to the phone cct. A simple on/off switch on the supply to the whole thing was operated as required. To obtain any cadence, just change the cam ....

It will drive old or modern phones and has been in use now for over 20 years - never a failure!

Which in a basic form is precisely how the ring cadence used to be generated in each telephone exchange.

In fact the same machine drove different cams on the same shaft which supplied ALL of the different tones as well - dial tone, interrupted dial, busy, equipment busy, ring tone etc etc.

[daifuse]

Which in a basic form is precisely how the ring cadence used to be generated in each telephone exchange.

In fact the same machine drove different cams on the same shaft which supplied ALL of the different tones as well - dial tone, interrupted dial, busy, equipment busy, ring tone etc etc.

 

Yes, being a yit* in the dim and distant past, that's where I got the idea

 

*yit = 'Youth-in-training' with GPO Telephones!

[KevinE]

Most bell telephones dont ring properly on 50Hz, as has been said already, it's about half that frequency.

 

Modern ring generators either use a switchmode design or you can actually use a small DPCO relay that's driven off an oscillator to swap the polarity...that's how the BT REN Booster works.

 

Our Teletron bench phone test kit uses a ringing voltage at 50Hz and the newer single-gong bells ring ok but the twin bell 300/700 series don't and certain electronic ringers dont like it either.

 

http://www.pmctelecom.co.uk/images/BT%20ring%20booster.jpg

[daifuse]

Most bell telephones dont ring properly on 50Hz, as has been said already, it's about half that frequency.

 

Hence the diode in my 'design'. It effectively reduces the frequency to a sort of 25Hz. It's fairly simple to adjust the bell in the older 'phones to get an acceptable result.

[KevinE]

It effectively reduces the frequency to a sort of 25Hz

 

Mm, well, A full bridge rectifier increases the ripple to 100Hz, so I suppose a single diode is only half that? It will still produce DC...a telephone bell requires AC

[Ynot]

Which in a basic form is precisely how the ring cadence used to be generated in each telephone exchange.

In fact the same machine drove different cams on the same shaft which supplied ALL of the different tones as well - dial tone, interrupted dial, busy, equipment busy, ring tone etc etc.

 

Yes, being a yit* in the dim and distant past, that's where I got the idea

 

*yit = 'Youth-in-training' with GPO Telephones!

How d' you think I knew...?

;) :D

[dvidos]

This guy had the idea to create an audio CD. You only need a spare power amplifier.

 

Maybe one could make the audio sample in CoolEdit or something, instead of C program?

 

Dimitris.

[daifuse]

It effectively reduces the frequency to a sort of 25Hz

 

Mm, well, A full bridge rectifier increases the ripple to 100Hz, so I suppose a single diode is only half that? It will still produce DC...a telephone bell requires AC

 

.....pulsed dc .... ?

[d_korman]

You DON'T want the phone to stop ringing when the handset is lifted, since if the talent does not replace the handset correctly afterwards and the phone has to ring again you are in trouble. It's happened to me more than once. You generate the ring pattern manually and just watch for the handset to be lifted.

Don't quite see what you're saying here...

Few phones (if any) will ring at all with the handset off hook, so how do you get it to do so if they DON'T replace the h/s properly?

And to be honest it makes little difference whether you send the ring cadence automatically or manually - the phone will either ring or it won't...

 

On most modern phones the ringer does not pass via the hook switch - the exchange detects that the handset has lifted and cuts the ring signal. Old type bell phones can easily be rewired to work the same way as there's a convenient terminal block inside which gives direct access to the bell coils.

[Wrighty]

On most modern phones the ringer does not pass via the hook switch - the exchange detects that the handset has lifted and cuts the ring signal. Old type bell phones can easily be rewired to work the same way as there's a convenient terminal block inside which gives direct access to the bell coils.

 

I'm not sure about that... My telephone ringer doesn't have anything special to detect the handset being lifted. On every phone I've tried (from ancient bakelite with fabric cord to several modern offerings), the ringing stops when the handset is lifted and continues when you put it back down. I was hoping to add some circuitry to detect when the handset was lifted, to automatically cancel the ringing, but I didn't have time before the unit was required for a job, so I had to go with it.

 

I see the Precision Vision one is £200... I wonder how many they've sold at that price, as I think I could do mine for a lot less.

[KevinE]

The 706 diagram is here;

 

GPO 706

 

On-board links choose whether the hook switch disconnects the bell on going off-hook, they're normally sent out this way on standard automatic exchanges and so if ringing voltage is continuously applied from a simlator, the phone will certainly stop ringing when you answer it as wrighty says..though it may cause a nasty buzzing through the earpiece which may be audible to the audience unless the ringer simulator is turned off manually when they answer.