| 摘要 |
PURPOSE:To make it possible to connect either of make contact system or break contact system, by generating a pulse either when the switch button of doorphone is turned on or when turned off. CONSTITUTION:In a key telephone system by which plural extention telephone lines are connected to the main equipment which has switching function, doorphone subsidiary equipments 3-1, 3-2 which are similar to interphone is connected to the main equipment through a doorphone speech control circuit 12. A button switch (s) of the doorphone is connected to a pulse generating device which is composed of comparator circuits CT1, CT2, inverters IC1, IC4 and flip-flips IC2, IC3. The pulse generation device generates a pulse when the switch (s) is turned from off to on, or from on to off, and sends it to a CPU9. The doorphone subsidiary equipment is connected to the telephone line through the doorphone speech control device according to the control of the CPU9. |
