Importance

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Abstract

Full duplex local intercom circuit arrangements are provided for telephone station instruments within a local network. Each instrument includes an FM receiver and an FM transmitter. If two subscriber telephone paths are provided, switches are also provided to reverse the connection of the paths of e.g. the calling party station relative to called party stations. The switches may be manual or automatic. If a single subscriber telephone path is provided, alternative carrier frequencies are selectively generated, with the calling party receive and transmit frequencies being reversed for the called party frequencies, either automatically, or manually. In all arrangements, the establishment of a normal telephone circuit through the central office over the subscriber line(s) has no effect on intercom communications, and vice versa.

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First Claim