PURPOSE: To simplify the circuit constitution, by transmitting the callout signal and control signal from the main device to each telephone set through the use of a single signal line.
CONSTITUTION: Each of a plurality of telephone sets TL1∼TLn connected in parallel with the main device ME, is provided with circuits A1∼An which amplify the callout signal from the main device ME and speakers SP1∼SPn, and callout signal and control signal for the amplifying circuits are transmitted from the main device ME. Further, single signal lines L1∼Ln are provided to each telephone set from the callout signal source SG of the main device ME, and a DC potential source for the control signal in the main device ME is connected to signal lines via a gate TR0. when the production of callout signal is started, the gate TR0 is controlled and the signal source SG is operated, and the callout signal and the control signals are transmitted with single signal lines.
YOSHIZAWA KENSAKU
NOZAWA MAMORU
KOBAYASHI TSUNEO
SASAI MINORU
KATOU MASAAKI
TANABE JIYUUICHI
OOSHIMA SETSUO
TAIKO ELECTRIC WORKS LTD
HASEGAWA DENKI SEISAKUSHO
IWATSU ELECTRIC CO LTD
KANDA TSUSHIN KOGYO KK
MEISEI ELECTRIC CO LTD
NAKAYO TELECOMMUNICATIONS
NITSUKO LTD
| JPS5357703A | 1978-05-25 | |||
| JPS5234601A | 1977-03-16 |