| 摘要 |
PURPOSE:To enhance the function of the key telephone system by securing the cordless part between the main device and the key telephone of the key telephone system as well as having multiplication of the signal. CONSTITUTION:Among the signals transferred between the main device and the key telephone, such signals which never occur at one time and are required for talking action as the call signal, the hook signals beofre and after the call signal, the dial signal, the incoming signal and other like in the case of the normal telephone are referred to as the first signal. And the signal which can be generated simultaneously with the first signal and is proper to the key telephone system is referred to as the second signal. These first and second signals are multiplied in the form of upper and lower side bands 6 and 7 which gave the smooth modulation to sum signal 3 and the differential signal of the first and second signals via subcarrier signal 7 of double pilot signal 4. The multiplied signals are then modulated by main carrier wave 2 to be transferred between the main device and the telephone. |
