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A digital current loop uses the absence of current for high (space or break), and the presence of current in the loop for low (mark). [1] This is done to ensure that on normal conditions there is always current flowing and in the event of a line being cut the flow stops indefinitely, immediately raising the alarm of the event usually as the heavy noise of the teleprinter not being synchronized ...
A major application of current loops is the industry de facto standard 4–20 mA current loop for process control applications, where they are extensively used to carry signals from process instrumentation to proportional–integral–derivative (PID) controllers, supervisory control and data acquisition (SCADA) systems, and programmable logic ...
Starship featuring Mickey Thomas in 2010. Starship was let go by their record label RCA and became inactive in 1991. [11] In early 1992, Mickey Thomas revived Starship as Starship featuring Mickey Thomas and touring has continued with this title. [12] [13] The band's Loveless Fascination was released on September 17, 2013.
The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems.
Keying is a family of modulation forms where the modulating signal takes one of a specific (predetermined) number of values at all times. The goal of keying is to transmit a digital signal over an analog channel.
"Practical Costas loop design" (PDF). RF Design. Electronic Design Group. Archived from the original (PDF) on 2012-02-11; Nicoloso, Steven P. (June 1997). An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Multipath Mobile Environments (PDF). Thesis (Thesis). Virginia Polytechnic Institute and State University.
At the remote end, the sent current flows through both solenoids in the same direction and into the termination load. Since current flows the same way in both solenoids the remote signal relay is activated by this local key. For the Diplex, a different trick is used. To send two messages simultaneously, one has two independent local telegraph keys.
Two-wire circuits in new installations are limited to intercom and military field telephone applications, though these too are being supplanted by modern digital communication modes. To communicate in both directions in the same wire pair, conversion between four-wire and two-wire was necessary, both at the telephone and at the central office .