Improvements in telephone apparatus

1,048,251. Pulse sending equipment. SHIPTON ELECTRONICS Ltd. July 22, 1963 [April 25, 1962], No. 15750/62. Heading H4K. Telephone dialling pulse sender includes a pulse generator and a counter which, upon counting the number of pulses representing a digit of a multi-digit number set up for sending, operates a pause circuit to stop the generator for an interdigital pause period during which the counter is reset to zero and its output circuits set up for the succeeding digit. The Figure shows a loud-speaking telephone circuit equipped with the pulse sender according to the invention. In order to set up a call a key such as K1, of which there is one for each line in the system, is operated. Key K1 has three digit contacts B, C and D, corresponding to the respective digits of the number required, and an A contact which, when closed, operates a relay 13 to loop the exchange line to indicate a calling condition, and also applies H.T. to the various circuits of the apparatus. Dialling tone from the line is applied to a dial tone detector circuit 5 and causes normally conducting transistor Tr 5 to be cut off to allow capacitor C14 to charge. After two seconds of dialling tone the voltage on C14 is such as to trigger the dial trip circuit 6 which, via gate 17, cuts off transistor Tr8 and allows the dial pulse generator 7 to operate and, via relay 16, send dialling pulses to the line. Dialling pulses are also applied, via line 21, to the counter 10 which steps on until the number of pulses counted is such as to energize one of the coincidence lines 10b which is connected to contact B of the selected switch K1. When this line is energized the pause circuit is operated, over line 23, and this, via gate 19, allows transistor Tr8 to conduct to inhibit the dial pulses. The pause circuit also, via line 25, resets counter 10 to its initial condition and applies a stepping pulse to the sequence counter 11 which inhibits the action of the counter output connected to contact B of switch K1 and enables the counter output connected to contact C of switch K1. At the end of the pause period the dial pulse generator 7 is enabled via gate 18 and the pulses corresponding to the second digit of the required number are counted out as for the first digit, the action is then repeated to enable the third digit, selected by contact D of switch K1, to be dialled out, at the end of which the pause circuit, in resetting sequence counter 11, causes the final circuit 9 to be triggered, to remo