BT phone box idea looking for advise

[andybarrett1]

Hi Thank you for reading

 Am still looking at a future idea... Involving an old BT Telephone Mech.

 I need the existing "Dial" to give me one digital pulse for each digit dialled..... :-

 As I understand it at the moment the number 6 for example is dialled
 As the dial rotates back to its rest position I will get a pulse train of six pulses ......Hi Hi Hi Hi Hi Hi ..... for 4 I will get four pulses as it rotates back ...Hi Hi Hi Hi.....etc
 How might I convert these pulses into single pulses ... one for each digit dialled.

 The BT Phone box (K6)in question is a UK listed landmark and needs to stay as authentic as possible.

 Otherwise would just use PB switches

 Help / Advice Welcome

 BR
 Andy

[fourtytwo42]

In a strowger exchange that would be the slugged CD relay. Depending on whether you want your exchange equipment from the same era you either need a strowger selector from somewhere (expensive) or do it in software on an MPU or use a simple logic monostable.

[andybarrett1]

I like the idea of a logic monostable.... Maybe get the 74 series books out lol

Thank you

[Ian.M]

IIRC on a classic GPO rotary phone dial mechanism, there is an auxiliary contact that indicates whether or not the dial is in its home position.  I think it was used to mute the earpiece while dialling.

OTOH if you are limited to hooking up to the two wire line interface of the phone, you'll have to detect the dial's pulsed interruption of the line circuit.