Relay

Relay is also the name of a series of medium-altitude satellites; the first of which was launched in 1962.

Related Topics:
Satellite - 1962

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A relay is an electrical switch that opens and closes under control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. It was invented by Joseph Henry in 1835. Because a relay is able to control an output circuit of higher power than the input circuit, it can be considered, in a broad sense, to be a form of electrical amplifier.

Related Topics:
Switch - Electromagnet - Joseph Henry - 1835 - Amplifier

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These contacts can be either normally-open, normally-closed, or change-over contacts.

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• Normally-open contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive.
• Normally-closed contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive.
• Change-over contacts control two circuits: one normally-open contact and one normally-closed contact.
 
Relay: Operation ►