<P> In the UK , a brief excursion from standards , GPO telecoms introduced in 1968 their first push - button telephone , the GPO 726 ( Ericsson N2000 series ) , that used neither pulse dialing nor DTMF tones . It used a DC signalling system comprising a number of rectifier diodes arranged in different polarity configuration according to the button pressed . The 726 also requires a ground wire as well as the usual A and B wires . The irony was that with the few installations , the dial signal still had to be converted to pulses in the host PABX . It is now a rare device . </P>
<P> In the UK , a brief excursion from standards , GPO telecoms introduced in 1968 their first push - button telephone , the GPO 726 ( Ericsson N2000 series ) , that used neither pulse dialing nor DTMF tones . It used a DC signalling system comprising a number of rectifier diodes arranged in different polarity configuration according to the button pressed . The 726 also requires a ground wire as well as the usual A and B wires . The irony was that with the few installations , the dial signal still had to be converted to pulses in the host PABX . It is now a rare device . </P>
when did push button phones come out in the uk
when did push button phones come out in the uk
1968
1968