Line/interface circuit for key telephone systems

Details Line/interface circuit for key telephone systems Line/interface circuit for key telephone systems

1978-07-13

1980-06-10

Moffitt, James W.

H04M 172

Patent

active

042074398

ABSTRACT:
A line/interface circuit for a key telephone system, which system is of the type including a subscriber telephone line manifesting a pair of conductors. The conductors emanate from a central office or PBX and the line/interface circuit provides interconnections between a key subset associated with said subscriber and said central office via said telephone line. The line/interface circuit has optical sensing means for producing a signal indicative of ringing to indicate an incoming call. Means are coupled to the optical sensing means to access the subset with an alternate signal. The subset is coupled for the transmission of voice signals to the telephone lines by means of a transformer to provide isolation. Additional means are provided to enable operation of the subset in a hold condition without releasing a connection between a connected party and the subset. The line circuit provides additional means to enable the subset to initiate a call by accessing the telephone lines, which access is accomplished rapidly with a minimum of interferences in regard to the telephone lines. Due to the nature of the coupling and operation of the line circuit, the line circuit performs all required switching and supervisory functions with a minimum of interference to the telephone lines, thus avoiding the use of an interface.

REFERENCES:
patent: 3916118 (1975-10-01), O'Neill
patent: 3925624 (1975-12-01), Earle et al.
patent: 4004106 (1977-01-01), Yachabach et al.
patent: 4039763 (1977-08-01), Angner et al.
patent: 4079212 (1978-03-01), Sasai
patent: 4101740 (1978-07-01), Barsellotti
patent: 4101741 (1978-07-01), Kunstatter
patent: 4125749 (1978-11-01), Kinoshita et al.
patent: 4132870 (1979-01-01), Liu
patent: 4145579 (1979-03-01), Angner et al.

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