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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 ...
A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the ...
IARU Region 1 is encouraging individual beacons to move to 50.4 MHz to 50.5 MHz. [4] [5] In the United States, the Federal Communications Commission (FCC) only permits unattended 6-meter beacon stations to operate between 50.060 and 50.080 MHz. [6] Amateur beacons at 50 MHz have also been used as signal sources for academic propagation research [7]
A schematic of a superhet AM receiver. Note that the radio includes an AGC loop in order to maintain the RF and IF stages in their linear region, and to produce an audio output not dependent on the signal power received. Here we show block diagrams for typical superheterodyne receivers for AM and FM broadcast respectively.
In telecommunications, a four-wire circuit is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction only by one path and in the other direction by the other path. The four-wire circuit gets its name from the fact that is uses four conductors to create two complete electrical circuits, one for ...
WQDR-FM's studios and offices are on Highwoods Boulevard in Raleigh. [4] The station's transmitter is off Business Route 70 in Garner . [ 5 ] WQDR-FM is a Primary Entry Point (PEP) station for the Emergency Alert System , and was previously the Common Program Control Station (or CPCS-1) for the Raleigh operational area of the Emergency ...
A standard frequency and time signal service is a station that operates on or immediately adjacent to 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, and 25 MHz, as specified by Article 5 of the ITU Radio Regulations (edition 2012). [2]