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 | | Relays, Cradle |
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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.
These contacts can be either Normally Open (NO), Normally Closed (NC), or change-over contacts.
- Normally-open contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. It is also called Form A contact or "make" contact. Form A contact is ideal for applications that require to switch a high-current power source from a remote device.
- Normally-closed contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. It is also called Form B contact or "break" contact. Form B contact is ideal for applications that require the circuit to remain closed until the relay is activated.
- Change-over contacts control two circuits: one normally-open contact and one normally-closed contact with a common terminal. It is also called Form C contact.
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| Bronze Partners |
| Alarm Controls Corp. |
| Allied Controls Acquisition Corp. |
| American Zettler |
| Americor Electronics, Ltd. |
| Aromat Corp. (Matsushita Electric Works, America) |
| Line Electric Products |
| Magnecraft |
| Master Electronic Controls (MEC) |
| MEDER electronic Inc. |
| Pontiac Coil-Arkansas |
| Universal Relays |
| Books |
Cradle
Gentry Lee and Arthur C. Clarke
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| Excerpt - page 326: "... to receive a beam would trigger the opening of a relay. When both relays were open, current could flow ..." | | See more references to Relays, Cradle in this book. |
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The Library of Alexandria: Rediscovering the Cradle of Western Culture
Roy MacLeod
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Configuring Cisco Voice Over IP
Jason Sinclair, Paul Fong, Scott M. Harris, and Martin Walshaw
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| Excerpt - page 81: "... not release unless the telephone goes on-hook and the Alpha relay has been released for 200 milliseconds. This is how the CO knows when a conversation has ended and the receiver has been placed into the cradle. The last relay, which we will call Charlie, energizes when ..." | | See more references to Relays, Cradle in this book. |
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