| Patent Number |
Title Of Patent |
Date Issued |
| 4086570 |
Controlled DC current supply device with open circuit detecting means |
April 25, 1978 |
| A control system of the type used in process control and comprising a controller which provides a control signal on a signal line, and a DC output circuit for converting the control signal on the signal line into a DC current output signal varying in a range of, e.g., 4 to 20 milliam |
| 4082942 |
Process control system with signal conversion to standard intermediate signals carrying data as |
April 4, 1978 |
| A process control system of the type arranged to accept varied forms of analog sensing signals from field sensing devices, to digitally process data represented thereby, and to supply varied forms of analog control signals to field control devices. The system is characterized by signal |
| 4074354 |
Process control system |
February 14, 1978 |
| A process control system of the type arranged to accept sensing signals from field sensing devices, to digitally process data represented thereby, and to supply control signals to field control devices. The system is characterized by a centralized maintenance backup system for supplying |
| 4013975 |
Variable resistance circuit |
March 22, 1977 |
| A variable resistance circuit comprising a field effect transistor, a plurality of amplifiers and a feedback circuit for one of the amplifiers with the equivalent resistance value derived from a circuit comprising the field effect transistor electrodes and a reference resistor being |
| 3959772 |
Two-wire signal transmission system |
May 25, 1976 |
| A signal transmission system of the type used in process control systems for conveying a signal between a field telemetering instrument and a central controller, or between a central controller and a process control device. The signal transmission system is arranged with a transmitter |
