| 摘要 |
PURPOSE:To prevent fault when ineffective release left undone by releasing the priority setting state automatically depending on the change in the hook state of a telephone set subjected to priority setting. CONSTITUTION:A branching circuit 3 has a voice/control signal line 2b, a power line 2c, a hook signal line 2a between a radio equipment 2, has a required line between a main telephone set 4 and a slave telephone set 5 and is provided with a priority setting switch section 6. In depressing a contact S1 of the switch section 6, the output of the FF 32 is inverted, a level Q goes to H, a transistor TR1 is turned on, contacts ra, rb, rc of a relay 31 are opened, the slave telephone set 5 is disconnected from a radio equipment 2 and only the master telephone set 4 is in the priority setting state. When the master telephone set 4 finishes the talking and hooks on, the change in the hook signal is detected by a differentiation circuit 33, the FF 32 is reset and the priority setting state of the main telephone set 4 is released.
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