Hi, they Yes, it's definitely DTMF....it even has "*" and "#" buttons either side of the "0", unlike any other Trimphones I've seen in the wild. According to the label on the bottom of the broken one, it was supplied by BT rather than the GPO. There's nothing indicating any date of supply or manufacture though. A friend got these phones for me around about 1989/90. He was on an industrial placement at Kidsgrove I think (working for either ICL or STC) and came across an entire skip full of the things next to an office block which was being refurbished. I guess they were used on an internal exchange? BTW Any idea when BT started "DTMF enabling" exchanges (presumably that came in with "System X")? I've got a vague recollection of requesting tone dialling around 1988 give or take a year, and having to have my number changed since only one of the five exchanges covering this area at the time was a System X exchange. Thanks, I'll go take a look. Well, I'm not sure it's just the ringer....when the phone was plugged into the line and someone called the (trim)phone on my extension would completely fail to ring. Also, the exchange would send them a single ring tone, then a few seconds of silence (as if the call had been answered), then another single ring....etc.... I suppose I should sit down and trace out the circuits. Most of the "complicated" stuff seems to be on the keypad (the DTMF encoder), the rest looks fairly straightforward. Just a matter of getting up the enthusiasm, not easy at the moment as I'm still fighting off the effects of coming off anti-depressants.... :-( TTFN - Pete.