delay circuit[di′lā ‚sər·kət]
an electronic simulation device for reproduction of a signal with a delay equal to a predetermined time interval τ. Delay circuits are used in the simulation of technological processes associated with matter transfer or the channeling of power, in the approximation of equations describing complex objects, and as a component of certain automatic control and monitoring systems. For example, using a delay circuit connected to an electrical network it is possible to record not only a breakdown of the network but also the process preceding the occurrence of the breakdown. In actual practice τ can vary from fractions of a second to dozens of minutes. The operation of a delay circuit is based on the use of magnetic recording, the capability of electrical capacitors of retaining a charge, and an approximation of the transfer function in an ideal delay component.
In a magnetic delay circuit the time delay is proportional to the distance between the recording and playback heads. The delay is also inversely proportional to the linear speed of the data carrier. In capacitor delay circuits, signals are “memorized” in the form of an electrical charge of the capacitors that is proportional to the voltage level supplied to the circuit. The process of memorizing (delay) consists in the sequential switching of the voltage (signal) to the capacitors or the sequential transmission of the voltage through a series of capacitors. The data thus delayed are reproduced by sequential connection of the charged capacitors to a voltage indicator (a voltmeter or oscillograph) or are read out by recharging thfe last capacitor in the series. The delay time of a delay circuit is proportional to the number of capacitors and inversely proportional to the switching frequency. Electromechanical systems limit the ultimate switching speed and decrease the reliability of delay circuits; therefore, their use is feasible only for low-frequency input signals.
REFERENCESKogan, B. la. Elektronnye modeliruiushchie ustroistva i ikh primenenie dlia issledovaniia sistem avtomaticheskogo regulirovaniia, 2nd ed. Moscow, 1963.
Doganovskii, S. A., and V. A. Ivanov. Bloki reguliruemogo zapazdyvaniia. Moscow-Leningrad, 1960.