A system for screening out undesired signals from desired signals, the system being selectively programmed to effect this screening through programmed codes, the system also having means to utilize the desired signals to effect the performance of a selected function such as the sounding of a signalling...http://www.google.fr/patents/US4006316?utm_source=gb-gplus-shareBrevet US4006316 - Code-controlled detection and function actuating system
Code-controlled detection and function actuating system
