To provide a wireless headset from which a call switch and switches for turning up and turning down a receiving volume are removed, a helmet using the wireless headset, an Internet telephone system, an on-board hands-free system, a communication system, a credit processing system, and a cash service system.
Voice of a speaker is inputted to a microphone 2, and an output by comparing an output signal of the microphone 2 with first reference data at a controller 9 makes a telephone off-hook. While a telephone call is in progress, call data is compared with second reference data at the controller 9, and according to the difference, an amplifying degree of a second amplifier 8 which drives a speaker 3 is made variable. When voices of the party on the other end and a speaker are lower than a specified value, the speaker 3 sounds an alarm, and the telephone is made on-hook after a lapse of a predetermined time.
ITO MAMORU
KATSUKAWA TADASHI
OHASHI TOSHIHIKO
MITANI YASUSUKE
