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POTS telephone line ringer

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KamalS

New Member
I want to ring my POTS telephone line "in house."

Here is what I want to do:

I have a number of telephones connected in parallel to the main telephone line.

If I can superimpose the ringer tone required onto the main telephone line (it carries 120V when idle), I can make all the phones ring - an elementary intercom - but powered completely from the main telephone line.

NOTE : I do not need to generate 120V as that is already present on the main telephone line - I need to "somehow" impose the ringing signal (connect the ringer via a cap or high valued resistor or diode or all of these?).

A simple ringer that can be powered from the main telephone line without loading it too would be appreciated (maybe a 5V1 zener across a 555 timer or something)

Any ideas/suggestions/working circuits?
 

MikeMl

Well-Known Member
Most Helpful Member
It has been years since I played with this, but as I remember, the hung-up voltage is ~49V DC line to line. Off hook, it drops to ~10V. While ringing, there is 100VAC superimposed on the 49VDC. The ringer has a capacitor in series with the ringer, causing the ringer to ignore the DC. The ringing voltage is ~10Hz, and the ringer clapper resonated mechanically at the ringing frequency.
 

MikeMl

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Most Helpful Member
I'm quoting the US standard. I just went and measured it. On-hook, not ringing = 52.4V, green to red. I've forgotten the test number that rings your own phone, so I couldn't measure the ringing voltage. I guess if that call-back ring number worked in your area, you wouldn't have to build anything :D
 

audioguru

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Most Helpful Member
The telephone ringing frequency in North America is 20Hz at 90VAC, superimposed on the -50VDC.

I think the telephone system in Kamal's country or planet is completely different.
 

marcbarker

New Member
Back in early 80's I designed and manufactured a batch of POTS line simulators for testing telephone answering machines. I might have a schematic somewhere if you don't mind waiting. I used a transformer somehow to couple the ringing signal into the 'Line'.

In UK, the line it's about 48 VDC with phones on-hook.

AC Ringing signal is applied to one of the twisted pair only, referenced to ground. (there's a historical reason why this is, to do with party lines)

Traditionally, a DC blocking capacitor and bell in series is across the Line.

The ringing voltage is impedance-limited, they call it REN here. I can't remember the voltage, I think it's 100 V pk-pk and 20 Hz.

Off-hook the phone is something like 600 Ohm, and a DC current flows of I think it's 40 mA, I might be wrong.

If you ever send a Ringing Signal from Home into the Telephone Company they will be annoyed at you, it damages zener barriers in their infrastructure.
 

KamalS

New Member
I have got the callback number. There are a few things that discourage me from using it:

1. After dialling that number I need to wait until a high pitched horrid tone blasts out of the telephone receiver
2. I need to wait a minute for the call to come
3. When I/someone picks up the phone now, the VERY same high pitched horrid tone blasts out of the telephone receiver.
4. I can't disconnect the phone if I suddenly decide to cut the call... I HAVE to receive the call AND be damned with "the high pitched horrid tone blasts out of the telephone receiver".
5. The calls are charged as two units each and are not free.

marc, it's ok as long as it does not use a transformer :)

I believe that the power of my ringer will not be that high to affect the box 200 feet away from my home phone terminal ;-)

what about the suggestions I gave - do they make sense?
 

tcmtech

Banned
Most Helpful Member
I dont know if it still works but you used to be able to just dial your own phone number then hang up. About two seconds later the phone would ring. Its how we used to talk back and forth from house to out building without leaning out the door and shouting the 200+ feet!
 

marcbarker

New Member
I believe that the power of my ringer will not be that high to affect the box 200 feet away from my home phone terminal ;-)
It certainly will be if it's still connected at the time.


Can't you instead use a Cellphone to call Home?
 

audioguru

Well-Known Member
Most Helpful Member
My telephone exchange is digital now:

I cannot dial my own number, hang up and have it ring anymore.
I cannot dial a special number, hang up and have it ring anymore.
I cannot call somebody then make their phone line busy forever if I do not hang up anymore (some businesses did that to competitor's phone lines).

I pay a monthly fee for my telephone line. Local calls are free. Incoming calls are free. Outgoing long disance calls are charged by the second from the time the distant caller answers.

My telephone lines, cable TV and high speed internet cable, electricity wires, natural gas pipe and sewer pipes are hidden under the ground.
 

mvs sarma

Well-Known Member
My telephone exchange is digital now:

I cannot dial my own number, hang up and have it ring anymore.
I cannot dial a special number, hang up and have it ring anymore.
I cannot call somebody then make their phone line busy forever if I do not hang up anymore (some businesses did that to competitor's phone lines).

I pay a monthly fee for my telephone line. Local calls are free. Incoming calls are free. Outgoing long disance calls are charged by the second from the time the distant caller answers.

My telephone lines, cable TV and high speed internet cable, electricity wires, natural gas pipe and sewer pipes are hidden under the ground.
1. Even in digital excahnges it is possible to get a self ring back. We call it faultsman's ring back. There is a code allotted for it. In India we have siemens EWSD systems, and French Alcatel.

Perhaps you mean your line is ISDN, Is it? in ISDN you can make two simultaneous calls, if it is 2B+D.\

the outgoing free calls for local-- whether in entire Canada or in the city you live in or whether within an exchange area?

your third condition has been cleared off even in analog switches since a long time
it is called Called part held alarm.It was existing even in the strowger type electromechanical exchanges, almost since 1965, ( the time i joined telecom) after a predetermined time the connection gets disconnected and the called party freed. an old principle.after Cellular systems came up , call it the CDMA or GSM, the moment called party disconnects, the call is abandoned. and the phone is free.
 
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audioguru

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Most Helpful Member
Hi Sarma,
I don't have ASDN.
I think all of Canada and America have free local calls (but there is a monthly fee for the telephone line even if it is not used).

I refuse to pay extra for DTMF so my telephone line is still rotary dial pulses. My pushbutton phones have a switch for DTMF for me to do banking after the bank answers.
 

mvs sarma

Well-Known Member
Hi Sarma,
I don't have ASDN.
I think all of Canada and America have free local calls (but there is a monthly fee for the telephone line even if it is not used).

I refuse to pay extra for DTMF so my telephone line is still rotary dial pulses. My pushbutton phones have a switch for DTMF for me to do banking after the bank answers.
Thanks AudioGURU. it is good that you get free calls across US and Canada.
As of now there is NO specific charge for DTMF, for us in India, as of now.It was a story of past. I feel they should abandon the additional charge by augmenting the MF/DTMF registers in the various central offices. Even the telcos gain by this. It would save lot of time and missed calls due to finger slip, etc. the switches need hold that long to receive dialed information from the customer/subscriber, once the system has been updated by DTMF dialing.
 

audioguru

Well-Known Member
Most Helpful Member
My telco wanted to charge a fee to remove Call-Waiting service that had its price increased.
I said, "I am a senior citizen. My government buys medicines for me and my bank does not charge fees from me. Let me speak to your manager". The fee was cancelled without me talking to the manager.

I phoned my cable TV/internet provider and asked for the promotion that goes to new customers. They said no but gave me one month of free pay-per-view and a free upgrade to much higher speed internet for one month. They already billed extra for the free stuff because they bill in advance.
 

marcbarker

New Member
My telco wanted to charge a fee to remove Call-Waiting service that had its price increased..
It's probably too late now to suggest this: Ask the call centre person for authorisation to Waive the fee (as a goodwill offer).

I did this recently with my telco company, to waive the money outstanding on a final bill after I cancelled it, as a goodwill offer in return for my consideration returning to them as a customer.
 
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