Trimphone

After asking for something related to a DTMF Trimphone I have now in my grubby hands a 12 button Trimphone. It is a shade under par but lets see what happens.

Part one... The curly chords where rather sticky and the case dirty, taken it all apart and as I was filling the dishwasher anyway put the leads in there. Not wanting to melt the plastic bits (new leads are obtainable) they are now in soak with some 'Oxy cleaner' stuff the missus bought.

Photo attached is as received, BTW it worked first time upon plugging it in, sidetone a bit weak but the fast DTMF is much better than the modern house phones we have. Spent a few minutes tapping the transmitter to loosen the granules, not a lot of difference in resistance on my AVO so it is in the oven at 80C for an hour or so.

The resistance is compared with a 746 microphone which measured about 3k, the Trimphone one 500 ohms.

A setback, knocked the 'tit' off the transmitter and it's granules fell out. Oh well, probably needed an electronic transmitter anyway. Lesson learnt, use a proper spanner NOT a pair of pliers to screw the nut on!

As much progress as I can hope for 'till the new transmitter arrives. I must say it looks very good after a clean. It did come with a 'recall' switch, I don't need one so it's not fitted. If anyone wants one...

[Nickthedentist]

Nice to see my unloved Trimphone being treated to a bit of TLC. It's looking much more promising already. Could you post a pic of the insides? I never got as far as taking off the covers.

Nick

Nick (and all),

The insides, no cleaning needed at all. I have got a new microphone and line cord on order, and then I must wait for a call (ringback is a pain these days) to get the whole Trimphone experience (in modern parlance). People say 'ring from your mobile', I refuse to have one.

A couple of odd things I have noticed are the slightly yellow (upon close inspection) * and # keys, makes me think they are from different production runs. Also the 6 and 9 keys are identical and the 0 key is symmetrical. All keys are superb double injection mouldings, they will never wear out.

A proper bit of design, both technical and aesthetic, it's a keeper, the new kitchen 'phone.

[Nickthedentist]

Thanks, MM. I presume the DTMF IC is one of those Ferranti ones in a ceramic package?

I noticed the shade mismatch on the * and # keys too. I suspect the DTMF version was rarer than the LD one, so I suppose a large production run of the numerical buttons, and a smaller run of the others is likely.

Any clues as to the date? ISTR the BABT approvals label saying something about 1981.

BTW, you can usually get a phone to ring back by using a time break recall button (if fitted), or "flashing" the gravity switch, i.e. pick up the handset, make a call (121, the old Mercury access code seems to be ideal in some areas, otherwise phone a freephone number with a recorded message), then very briefly depress and release the handset cradle, and finally replace the handset

N.