CORDLESS TELEPHONE SYSTEM

• Main Author: YASUNO JUNICHI
• Format: Patent
• Language: English
• Published: 18.05.1990
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TELEPHONIC COMMUNICATION; TRANSMISSION; WIRELESS COMMUNICATIONS NETWORKS

PURPOSE:To adjust a detection level through simple circuit constitution by detecting the idle channel of a radio line by suing one comparison circuit, and besides, detecting whether distance between a child machine and a parent machine is within the communication limit of a carrier or not. CONSTITUTION:Before the radio line is formed between the parent machine and the child machine, a control circuit 15 controls the lacal oscillation frequency of a PLL circuit 11b so as to receive a channel intended to use, and simultaneously, controls a transistor(TR) 13d so that the signal of a comparatively higher level is inputted to a comparator 13e. Next, after the radio line is formed between the parent machine and the child machine, the control circuit 15 controls the TR 13d so that the signal of the comparatively lower level is inputted to the comparator 13e. In this case, since the level to decide whether the distance between the child machine and the parent machine is within the communication limit of that carrier or not is lower than the decision level of a background noise at the time when the carrier is not used, it can be detected whether the distance between the child machine and the parent machine is within the communication limit of that carrier or not. Thus, the cordless telephone system of the simple circuit constitution and simple adjustment can be realized.