Telephonic communications – Terminal accessory or auxiliary equipment – With circuit connection to terminal
Reexamination Certificate
2005-11-15
2005-11-15
Tran, Sinh (Department: 2644)
Telephonic communications
Terminal accessory or auxiliary equipment
With circuit connection to terminal
C379S161000, C379S168000, C379S169000, C379S184000, C379S443000, C379S399010
Reexamination Certificate
active
06965672
ABSTRACT:
An electronic switching system, comprising a common source of voltage to a plurality of user stations connected in parallel, an electronic means of connection to electrically connect a chosen user station to the common source of voltage, and a means of disconnection command with an optical coupler to control automatically the electronic disconnection of other user stations to the common source of voltage. A default user station is normally the chosen user station. There are means of separation of grounds for the chosen user station and the other user stations. In a preferred embodiment there is a cell for each user station, with each cell including in series a means for separation of the grounds, a means for electrically connecting terminals of the chosen station at boundaries of the source of voltage, a means for filtering a signal and for rectification of alternating current, a means for determination of a response time of the cell, and a means for command of disconnection including optical couplers to control the electronic disconnection of the source of the voltage to the other cells. The optical couplers preferably include a light emitting diode and a light receiving transistor. The optical couplers may be connected in series or in parallel. Preferably, response time is determined by a circuit in each cell containing at least one resistor and at least one capacitor.
REFERENCES:
patent: 3829619 (1974-08-01), Close et al.
patent: 4281220 (1981-07-01), Frailey
patent: 4825465 (1989-04-01), Ryan
patent: 5444772 (1995-08-01), Coker
Briney III Walter F
Tran Sinh
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