GPO Rotary Dial Trimphone.
 

I am thinking of buying a unrestored GPO rotary Dial Trimphone, are they compatible with the modern system, or do I need to carry out some modifications.
Any advice appreciated.

Ken G6HZG.

Re: GPO Rotary Dial Trimphone.
 

They work but you need to ensure that your line accepts pulse dialling, and note that the REN is very high, so really good ringing is only possible if there are as few other devices with ringers on the same line.

Re: GPO Rotary Dial Trimphone.
 

I believe the early models had a permanently luminous dial - I think that it is tritium. It is radioactive.

https://www.lightstraw.uk/ate/tao/tr...adiation1.html

take care

SEAN

Re: GPO Rotary Dial Trimphone.
 

Thanks Nick, we have just been updated by our internet and phone provider with fiber direct to the house and our phone now uses the internet.
So I assume any old phone with Pulse dialing will be a non starter:shrug:

Ken, G6HZG.

Re: GPO Rotary Dial Trimphone.
 

Unless you interpose a pulse-to-tone converter.

Re: GPO Rotary Dial Trimphone.
 

Ohh eer.....8-o
Thanks for that info. Sean

Re: GPO Rotary Dial Trimphone.
 

Just had a look at these on a large online auction site, all round the £50 mark8-o
Not sure I want a Trimphone that much:shrug:
Thanks all for the informed response
Ken G6HZG.

Re: GPO Rotary Dial Trimphone.
 

A design classic aesthetically but quite horrid to use. I've never liked them that much either.

Re: GPO Rotary Dial Trimphone.
 

Ken, PM sent.

Re: GPO Rotary Dial Trimphone.
 

I worked for the GPO as a Youth In Training in 69 - 70 assisted with the installation of quite a few trimphone's. We had to go back on several to swap out for 746's because they were not stable when dialing out. Later on in life I had a keypad trimphone at home which was easier to use but I got to really dislike the warble on an incoming call.

That said, they do make a fashionable addition to a home, especially as 70's furniture is now on trend.

Rog

Re: GPO Rotary Dial Trimphone.
 

I've seen one site that sells reconditioned ones with a BT plug, but I'm not sure if they are tone dial though.

Re: GPO Rotary Dial Trimphone.
 

I have a couple of the later ones with the non-glowing dial, and a push button one as well I think. The early dials were indeed slightly radio active, and I gather used a liquid filled tube around the dial. Not a problem with single instruments in the home, but a different matter when there are hundreds being stored in a scrap cage at the depot, awaiting disposal. ISTR reading somewhere that there was a limit on how many could be stored together in one place.

Re: GPO Rotary Dial Trimphone.
 

Don't worry too much about radiation from the dial in old Trimphones. Tritium has a relatively short half-life (less than 13 years) so given the average age of a vintage Trimphone, nearly all of the tritium will be gone by now. It was only a problem when large numbers of dials were being stored, as Tim says.

If your phone line does not support pulse dialling, you will still be able to use a vintage dial phone to receive calls, but the dial won't work. To make a call, use another tone-dialling phone on the same line to dial the required number, then pick up the vintage phone and hang up the modern phone, in that exact order. This is easiest to do if the modern phone is a cordless one; you can place them both together and quickly swap from one to the other. This method works without needing to buy a pulse to tone converter. If you do get one, you can dial numbers on the vintage phone for a more authentic experience.

You can find vintage push-button Trimphones with * and # keys - these ones support tone dialling on the latest phone lines. Push-button Trimphones with only numbers 1-9 and 0 are pulse dialling. If you have a phone with a tone/pulse switch you can set it to pulse and try it on your line to see if pulse dialling is supported.

You can also find modern reproduction trimphone lookalikes, with 'dials' that have the * and # and generate tones for use on modern systems.

Re: GPO Rotary Dial Trimphone.
 

Unfortunately mine are a sort of cat-sick green colour which I don’t think will ever be on trend.

Re: GPO Rotary Dial Trimphone.
 

Have faith Tim... if you sit your trimphone on a G Plan wall unit next to a cheese plant then you have what was the 70's in a perfect nutshell !

Rog

Re: GPO Rotary Dial Trimphone.
 

But you'll still have to put the handset down to have the spare hand needed to hold the phone body down while you dial. Style over ergonomics. Style can come back into fashion, but once the function is got wrong... And people paid extra, every month, for this.

I think the danger with the tritium was if the glass got broken. Inhaled traces are quite different in risk compared to merely being near the stuff in a sealed container.

David

Re: GPO Rotary Dial Trimphone.
 

The original carbon inset microphones are rubbish! They go crackly very quicky. They're the same mic as those used in some GPO headsets so spares are available. There's a 'tube-of-pastilles' line regulator within the instrument that can flap about too but oughtn't be a problem.

We had a Trimphone upstairs when I was a kid. I used to get a belt every now and again by touching the metal recessed screw that holds the handset together at the top, and my earthed metal table lamp. Turns out holds the mic in place and I'd be fiddling, likely: getting a tingle when making and breaking the loop off the ASTIC.

As others have opined, they're a case of style over substance and you'll have a job dialling single-handed, as the whole instrument will turn. And don't remove and chew the tritium dial backlight insert either, just in case...

Re: GPO Rotary Dial Trimphone.
 

Remember that a TRIMphone is likely to be old enough that it's gone through 3 haff-lives of the tritium already. So it's down to 1/8th of the activity it was when new.

My late father worked with tritium professionally at one point. When I got my first TRIMphone he took one look at the betalight tube and said :

'The biggest risk is that if the glass breaks it will cut you. The second risk is that the phosphor is probably mildly toxic. As for the tritium, the amount in that tiny tube will do you no harm at all unless you do something very silly with it'

So I treat the dials with care, but I will take them apart to clean/adjust the governor, etc.

Re: GPO Rotary Dial Trimphone.
 

I've heard that putting Blu-Tak on the feet will stop them from turning when dialling.

Re: GPO Rotary Dial Trimphone.
 

Cat-sick green? That's two-tone avocado! I don't think you've got a future in advertising, Tim...