There is provided a key telephone system for transmitting and receiving a dial number by a peculiar control signal between a main unit and an extension telephone. The system comprises: an extension telephone; a main unit; an analyzing unit for analyzing an audio signal; and a calling unit for calling...http://www.google.fr/patents/US4996708?utm_source=gb-gplus-shareBrevet US4996708 - Key telephone system adapted to respond to information stored in a portable outpulser
Key telephone system adapted to respond to information stored in a portable ...
