Pulse dialling device for an apparatus connected to a telephone line.

摘要

A relay (2) isolates, when unoccupied, the telephone line (1). During dialling and communication, the d.c. line current passes through an MOS transistor (6) placed in series with a d.c. regulation circuit (71-72). During dialling, a photocoupler (8) operates the transistor (6) in order to cause interruptions to the d.c. current. During communication, a relay (93) allows on the one hand the a.c. line current to pass through the primary of a transformer (92) whose secondary is connected to a modem (10) and on the other hand the input of the transistor (6) to be passed to a capacitor (63) so as to increase, in the a.c. mode, the impedance offered to the line (1) by the transistor (6). The invention applies in particular to fax machines and telematic terminals. <IMAGE>