| 摘要 |
PURPOSE:To attain connection even if all channels are busy by searching an idle channel in 2 stages of search levels to connect a handset and a base unit. CONSTITUTION:A detection signal NSQL is used to search an idle channel and when no idle channel exists, a detection signal NSQH checks whether or not an existing channel is used by other stations. In this case, since the detection signal NSQH has a higher threshold level with respect to a reception level of a FM signal Sd than that of the detection signal NSQL level, even if the channel is busy (the signal Sd exists) by the signal NSQL possibly, when the reception level of the signal Sd exits between the threshold level (0dBu) of the signal NSQL and the threshold level (12dBu) of the signal NSQH, the channel is not used for the signal NSQH (no signal Sd exists). Thus, the channel is opened and a handset 1 is connected to a telephone line 3 via a base unit 2. |
