| 摘要 |
PROBLEM TO BE SOLVED: To make the scale of the system small by minimizing power consumption of a curl-cordless handset of the system and avoiding interference between transmission and reception signals. SOLUTION: Transmission from a master set main body 3 to a curl-cordless handset 4 uses an ultrasonic wave 01 as a transmission medium and transmission from the curl-cordless handset 4 to the master set main body 3 uses a radio wave F1 as a transmission medium in the transmission/reception of a speech signal between the master set main body 3 and the curl-cordless handset 4. Thus, interference between transmission and reception signals is avoided, the need for a branching filter that has been required for a conventional system using a radio wave for a transmission medium of the transmission and reception signals and that copes with a radio wave, having a wide variety of electric field strength, is eliminated so as to make the size of the system small. Furthermore, since the transmission from the curl-cordless handset uses radio waves for a medium, consumption of a battery provided to the curl-cordless handset is minimized. |
