| 摘要 |
PURPOSE:To prevent confusion to be brought upon a call by devising the transmitter-receiver such that plural transmitter-receivers do not apply simultaneously ring tone notice in the case of callout for them and a transmitter-receiver starting ring tone sends a carrier. CONSTITUTION:The system consists of one set of transmitter 1 and selective call transmitter-receivers 2-1 - 2-3. A reception circuit 4 of the transmitter- receivers 2-1 - 2-3 receives a carrier of a selective call code sent from the transmitter 1 and a carrier sent from other transmitter-receiver via an antenna 3. A control circuit 9 detects a ring tone in a speaker 7 and the transmission circuit 5 sends the carrier via the antenna 3. When a radio signal resulting from the carrier send from other transmitter-receiver and received by the circuit 4 is carrier signal, a carrier sense 13 detects the carrier signal and sends it to the circuit 9. Thus, the fact of ring tone notice of the transmitter-receiver of its own equipment is surely discriminated and confusion to be brought upon to the call is prevented. |
