| 摘要 |
PURPOSE:To evade the collision of control signals caused on the control channels by using an exclusive master device to search the idle channels and to control the slave devices via the control channels and making other master devices perform calling jobs. CONSTITUTION:When a call signal is transmitted from a slave device S1 via a control channel, this call signal is received by a control device 7 and sent to a CPU 5. The CPU 5 performs the control to secure the call between the device S1 and a call master device P1 for example. Then the CPU 5 selects one idle channel and then a communication master device to make the device 7 transmit a call answer signal. Receiving this signal, the device S1 switches channels as designated and transmits a channel switch signal after processing. The switch signal is received by the device P1 and sent to the CPU 5. Then the CPU 5 makes the device P1 transmit a state display signal so that the device S1 can grasp the connection state to an outside line. Furthermore the CPU 5 controls a switching circuit 3 to connect the device P1 to an outside line 1. |
