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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 8th Apr 2024, 8:20 pm   #1
Gabe001
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Default GPO 332 telephone to VoIP, cheaply

This story starts when I went to a forum members house to purchase some vinyl. A gorgeous display of GPO phones caught my attention and I knew I wanted one.

A few days later I was the proud owner of a GPO 332, actually the export model to Portugal (AEP) but essentially a clone

It was described as working by the seller, and indeed it did. I still have my telephone line,but my ISP (Plusnet) contract is due for renewal soon, so the line will soon go. They do not offer a router with VoIP built in, so I'll be expected to make my own arrangements.

In any case, the microphone was fine and the pulse dialing worked with the standard BT line when connected through my ADSL filter. Ringing was nice and loud when I received a call, and sound quality was fairly decent. As you know, however, pulse dialing has limitations. You lose the * and the # keys, and navigating sub-menus is tricky.

The challenge here was to future proof the phone, on a hobbyist budget. The first step would be to get a pulse to tone converter. The second would be to set up to work with a VoIP service.

I am not a stranger to VoIP. I had adopted this technology about 10 years ago,when international calls were extortionately expensive, and before WhatsApp, Viber and Facetime made calls to friends and family overseas effectively free. For the last few years my VoIP box (an Obihai 110) had been in storage in the garage.

The cheap Chinese pulse to tone converter shown in the link arrived today, exactly 8 days after I placed the order. With postage and taxes, still about half the price of the 'dial a tone'.

https://a.aliexpress.com/_EQLjutp

Being a 2 wire system, it would require re-introduction of the ringing capacitor in the phone into the circuit.

I wasn't sure what changes the previous owner did to the phone, but I reversed what was done before and wired it as per instructions on:
https://www.britishtelephones.com/pstconv1.htm
for the GPO 332

Remove strap T10 - T11.
Remove strap T11 - T12.
Insert strap T8 - T9.
Insert strap T1 - T2.
Insert a 3.3K ohm resistor between T11 and T12.
Rectifier No. 205 (if needed) inserted between T6 & T5.
Red wire of line cord to T9.
White wire of line cord to T1.
Blue wire of line cord to T11.
Green wire of line cord to T3.

The following changes were made:
The pulse to tone converter only expects the red and white wire from the phone. I used a pvc coated mains cable instead which is the only 2 core wire I had. The thickness of the strands actually made things a bit easier.

1. The blue and green wire connections above in the phone were omitted
2. The strap T10 to T11 was retained to bring the ringing capacitor in the phone back in circuit (so that the phone can ring)

The red wire (brown in my case) was connected to the red wire terminal in the pulse to tone converter and the white wire (blue in my case) to the terminal below.

This was plugged into the phone socket in my Plusnet ADSL filter using the cable straight from my Dect phone, and it worked immediately. I could hear the tones at the end of the rotation and made a few test calls without issue. * And # and redial (rotate and hold 3,2 or 1 worked well too. Phone sub-menus could now be navigated. Calling my landline using my mobile phone triggered the phone to ring.

Interestingly, I'm not quite sure why, but it doesn't work when I plug it directly into the BTs master socket directly (without the ADSL filter) until I invert the red and green wires on the pulse to tone converter. Maybe the filter switches the connections around?

Some pictures. Apologies not the neatest of jobs but I had never worked on a phone before.

Many thanks to Philip who helped me get this far.
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Old 8th Apr 2024, 8:40 pm   #2
Gabe001
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Default Re: GPO 332 telephone to VoIP, cheaply

Now it was time to test it with VoIP.
I dug out my Obihai 110 from the garage. It supports 2 VoIP providers and a phone line. For a "future proofing' test, the line would not be required as it is assumed this will no longer exist.

The only connections would be the phone to the VoIP box and box to plusnet router.

The VoIP box was configured to work with Sipgate (they offer a free geographic phone number and can even port your old number) for incoming calls, and Easyvoip for outgoing calls. Both were set-up and configured by me in the past and the accounts were still active. The config instructions can be found online quite easily.

I unplugged the phone line from the ADSL filter and plugged the phone into the VoIP box via an adapter (see picture). The phone was connected to the Obihai.

I used my mobile phone to call my Sipgate number and the phone rang and worked, excellent.
I used the phone to call my mobile phone, and it worked too (with and without the 0044)!

So there we have it. The perfect marriage of old and new.

The pulse to tone converter works so well I've retired my Dect phone to the garage.

The Obihai is ready and waiting for when my phone line disappears (I'll port the landline number) and the GPO 332 phone has pride of place on my desk, and is fully functional.

My wife calls it "Lurch" because it looks right out of the Adams family.

The middle insert is a custom job. The emergency numbers don't work on VoIP unless you register your address which I haven't done yet.

Hope this helps someone. Posted as a success story as I consider it one, albeit a rather straightforward one.

Questions welcome, as long as they're not too technical. Also, do let me know if I made a mistake - this was the first time I worked on a phone.

Gabe
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Old 8th Apr 2024, 10:30 pm   #3
Lloyd 1985
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Default Re: GPO 332 telephone to VoIP, cheaply

That’s some very useful information there, and it looks as though my own 332 may get to be more than a decorative object someday!

Regards
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Old 9th Apr 2024, 7:23 am   #4
Gabe001
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Default Re: GPO 332 telephone to VoIP, cheaply

Thanks Lloyd. It obviously takes forever to dial out with a rotary dial, but it does work surprisingly well and it's a nice decorative item too.

I'm tempted to do one for my office at work, just to confuse the millennials and gen z ers.
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Old 15th Apr 2024, 1:33 pm   #5
Graham G3ZVT
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Default Re: GPO 332 telephone to VoIP, cheaply

I had to increase the "interdigit timer" on the ATA to cope with high digits of the dial.
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Old 20th Apr 2024, 7:01 am   #6
Gabe001
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Default Re: GPO 332 telephone to VoIP, cheaply

Quote:
Originally Posted by Graham G3ZVT View Post
I had to increase the "interdigit timer" on the ATA to cope with high digits of the dial.
Which pulse to tone converter does this pertain to Graham? This seems to be OK with all the digits.
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Old 21st Apr 2024, 12:36 pm   #7
PaulR
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Default Re: GPO 332 telephone to VoIP, cheaply

Quote:
Originally Posted by Gabe001 View Post
Thanks Lloyd. It obviously takes forever to dial out with a rotary dial, but it does work surprisingly well and it's a nice decorative item too.

I'm tempted to do one for my office at work, just to confuse the millennials and gen z ers.
I had one in my office when I was working. It was the bell ring that caused the most interest. It had a rotatone which made # and * possible together with last number redial.
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Old 21st Apr 2024, 7:18 pm   #8
Graham G3ZVT
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Default Re: GPO 332 telephone to VoIP, cheaply

Quote:
Originally Posted by Gabe001 View Post
Quote:
Originally Posted by Graham G3ZVT View Post
I had to increase the "interdigit timer" on the ATA to cope with high digits of the dial.
Which pulse to tone converter does this pertain to Graham? This seems to be OK with all the digits.
One of my homemade ones

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They work like the Rotatone, needing direct connection to the pulse and off-normal dial contacts.

Various Sipura/Linksys ATAs

Sure, if you dial furiously like a newspaper reporter calling his city-desk with a scoop, it probably won't time out
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Old 22nd Apr 2024, 8:53 am   #9
Gabe001
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Default Re: GPO 332 telephone to VoIP, cheaply

Oh ok Graham, I get it now. Thank you. I misinterpreted what you meant before as I couldn't work out the ATA acronym (sorry!). There seem to be many in telephony. I'll keep it in mind from when I reconnect to the VoIP service. So far the line is still viable so I'm plugged in to bt directly - no full fibre in my area yet so I'm relatively safe for now.

Last edited by Gabe001; 22nd Apr 2024 at 8:58 am.
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Old 23rd Apr 2024, 2:53 pm   #10
Richardgr
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Default Re: GPO 332 telephone to VoIP, cheaply

That was very neat!

Now just to put it in a cold, draughty hallway where the whole family can hear your conversation, and your father taps his watch
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