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A stepping relay is a specialized kind of multi-way latching relay designed for early automatic telephone exchanges. An earth-leakage circuit breaker includes a specialized latching relay. [clarification needed] Very early computers often stored bits in a magnetically latching relay, such as ferreed or the later remreed in the 1ESS switch.
Elevators are another common application - large relay logic circuits were employed from the 1930s onward to replace the human elevator operator, but have been progressively superseded with modern solid-state controls in recent years. Relay logic is also used for controlling and automation purposes in electro-hydraulics and electro-pneumatics.
Such a "reed pack" was able to store one decimal digit, encoded in a two-out-of-five code (74210 code variant) for easy validity checking by wire spring relay logic. Such an electrically latching reed relay requires continuous power to maintain state, unlike magnetically latching relays, such as ferreed (ferrite and reed relay) or the later ...
A latching switch is a switch that maintains its state after being activated. [1] A push-to-make, push-to-break switch would therefore be a latching switch – each time you actuate it, whichever state the switch is left in will persist until the switch is actuated again.
Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process control. [1] Each device in the relay rack would be represented by a symbol on the ladder diagram with connections between those devices shown.
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Mercury relays have also been produced as latching or impulse relays. The Lenning design uses a horizontal glass tube with two axially isolated pools of mercury. [2] A conductive stirrup can bridge these to make the connection. The relay is controlled by the stirrup being rotated in and out of the pool along the horizontal axis of the tube.
A solid state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. They serve the same function as an electromechanical relay , but solid-state electronics contain no moving parts and have a longer operational lifetime.