H04M1/30 - CPC Classification

Substation equipment, e.g. for use by subscribers; Devices for calling a subscriber Devices which can set up and transmit only one digit at a time

• H04M1/31 » by interrupting current to generate trains of pulses; by periodically opening and closing contacts to generate trains of pulses 0
• H04M1/50 » by generating or selecting currents of predetermined frequencies or combinations of frequencies 19