| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that a limit on mount area on a printed circuit board and the cost reduction of the printed circuit board are interfered because a call signal generating circuit and a message waiting signal generating circuit are separately provided in accordance with a subscriber circuit. SOLUTION: A DC voltage generating circuit (DCPW) 5 of the subscriber circuit 300 boosts a voltage from a key telephone system or a telephone exchange main body power supply, a modulation circuit (MOD) 1 modulates and interrupts the DC voltage from the DC voltage generating circuit (DCPW) under the control of an interruption control circuit (INT) 2, in the case of transmitting the call signal (RG), the interruption control circuit (INT) 2 controls the modulation circuit (MOD) to provide an output of a modulated sine wave for a prescribed period and in the case of transmitting a message waiting signal (MW), the interruption control circuit (INT) 2 controls the modulation circuit (MOD) to provide an intermittent output of the modulated sine wave for a prescribed period, and the transmission circuit of the call signal (RG) and the message waiting signal (MW) are shared resulting in a decrease in the mounted area on the printed circuit board configuring many of the subscriber circuits and a reduction in the cost of the printed circuit board. COPYRIGHT: (C)2006,JPO&NCIPI
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