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3927278 Direct-station-selection intercommunication and automatic holding circuit in a key telephone system  
Apparatus incorporated in an operator attended key telephone system for answering incoming calls to the key telephone system, placing such calls on hold, communicating with other key telephone sets...
3800098 KEY TELEPHONE SYSTEM TRANSFER ARRANGEMENT  
In situations where a large number of lines terminate at a key telephone station such as occurs when the station is used for call director purposes, it is often necessary to transfer a call...
3794776 KEY TELEPHONE SYSTEM TRANSFER ADAPTER CIRCUIT  
Transfer adapter circuits are combined with a key telephone system for extending telephone lines to a private intercom system without the need for individual pickup button positions on the key...
Matches 1 - 3 out of 3