| 摘要 |
PURPOSE:To prevent useless power consumption by supplying alternately the power to a transmission and a reception circuit depending on its operation and pause in a ping pong transmission system where the transmission and reception are performed alternately. CONSTITUTION:A transmission input is applied to a terminal 1 at the transmission, amplified by transistors (TRs) Q1, Q2 and transmitted to lines L1 and L2 via a transformer T. The reception signal from the lines L1, L2 at the receptions fed to a base of TRs Q3, Q4 via the transformer T and an output of TRs Q9, Q10. A switching signal at a terminal 3 goes to high level at the reception, a TRQ6 is turned on and a reference current I1 flows to a resistor R6. Thus, constant current sources aI1, bI1 and cI1 are operated and the reception circuit is activated. On the other hand, a switching signal at a terminal 3 goes to a low level and a reference current I2 flows via a resistor R5. Then the constant current source dI2 is activated and the transmission circuit is brought into the operating state.
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