Communications: electrical – Condition responsive indicating system – With particular coupling link
Patent
1978-10-18
1981-05-19
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
With particular coupling link
340171R, 340505, 340506, 340518, 340531, G08B 108
Patent
active
042688221
ABSTRACT:
In a system for determining the state of each of a plurality of bi-state devices located remotely from a central station, a group of resonant circuits is connected to a multi-frequency excitation source. A bi-state device is then connected to each resonant circuit. When a particular bi-state device is in one position and its corresponding resonant circuit is being excited by its resonant frequency, a maximum amplitude signal is produced by the resonant circuit. When the bi-state device is in the other position, a lesser amplitude signal is produced. The signal produced by each resonant circuit is fed to detection circuitry and in turn to display circuitry. Thus the state of each of the plurality of bi-state devices is indicated by the display circuitry.
The two wire line in addition may serve as a transmission medium for a DC control signal used for controlling a remotely located process control valve or for controlling other final actuators.
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patent: 4027286 (1977-05-01), Marosko
Caldwell Sr. John W.
Crosland Donnie L.
Dion, Jr. Lawrence J.
Karnakis Andrew T.
The Foxboro Company
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