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Schematic of an AGC used in the analog telephone network; the feedback from output level to gain is effected via a Vactrol resistive opto-isolator.. Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input.
Note that there is no AGC loop, but simply uses a high-gain IF amplifier which is intentionally driven into saturation (or limiting). For single conversion superheterodyne AM receivers designed for medium wave (AM broadcast) the IF is commonly 455 kHz. Most superheterodyne receivers designed for broadcast FM (88 - 108 MHz) use an IF of 10.7 MHz.
An electrical grid may have many types of generators and loads; generators must be controlled to maintain stable operation of the system. In an electric power system, automatic generation control (AGC) is a system for adjusting the power output of multiple generators at different power plants, in response to changes in the load.
An example of a closed-loop block diagram, from which a transfer function may be computed, is shown below: The summing node and the G(s) and H(s) blocks can all be combined into one block, which would have the following transfer function: () = + ()
The Block I AGC initially had 12 kilowords of fixed memory, but this was later increased to 24 kilowords. Block II had 36 kilowords of fixed memory and 2 kilowords of erasable memory. The AGC transferred data to and from memory through the G register in a process called the memory cycle. The memory cycle took 12 timing pulses (11.72 μs).
The receiver records the Morse code on paper tape Generic block diagram of an unamplified radio receiver from the wireless telegraphy era [25] Example of transatlantic radiotelegraph message recorded on paper tape by a siphon recorder at RCA's New York receiving center in 1920. The translation of the Morse code is given below the tape.
A block diagram is a diagram of a system in which the principal parts or functions are represented by blocks connected by lines that show the relationships of the blocks. [1] They are heavily used in engineering in hardware design , electronic design , software design , and process flow diagrams .
Automatic gain control, intentional non-linearity and incidental non-linearity limit the output amplitude in various implementations of the oscillator. The circuit shown to the right depicts a once-common implementation of the oscillator, with automatic gain control using an incandescent lamp.