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| MIL-R-5757H
Contact, closed: A normally-closed contact with the relay released is a closed contact. A
normally-open contact with the relay operated is a closed contact.
Contact, open: A normally-closed contact with the relay operated is an open contact. A normally-open
contact with the relay released is an open contact.
Contact arrangement: The combination of contact forms that make up the entire relay switching
structure.
Contact bounce: Intermittent opening of contacts after initial closure due to contact impact.
Contact force: The force exerted by a movable contact against a mating contact when the contacts
are closed.
Contact gap: The distance between a pair of mating relay contacts when the contacts are open.
Contact weld: A contact failure due to fusing of closed contacts, resulting in their failure to open.
Cycle, relay: A relay cycle is defined as a relay pickup and dropout, (one opening and one closure of a
set of contacts). Therefore, a cycle consists of two operations.
Degassing: A process of thermally cleaning a relay (at elevated temperatures) to drive off harmful
gasses. Degassing is usually performed using vacuum pumps.
Dropout value (voltage), specified: As the current or voltage on an operated relay is decreased, the
value at or above which all relay contacts must restore to their unoperated positions.
Hermetically sealed relay: A relay contained within an enclosure that is sealed by fusion to insure a
low rate of gas leakage. This usually refers to metal-to-metal, or metal-to-glass sealing.
Hold value (voltage), specified: As the current or voltage on an operated relay is decreased, the value
which must be reached before any contact change occurs.
Miss: Failure to establish the intended circuit conditions (high or low output resistance, as applicable).
Normally closed contacts: Those contacts that are closed with the relay de-energized.
Normally open contacts: Those contacts that are open with the relay de-energized.
Operate time: The interval between the application of a step function input signal and closing of all
normally open contacts. Bounce time is not included.
Operation, relay: A relay operation is defined as when a relay changes from an initial condition to the
prescribed condition. For example, normally open to closed or vice versa. Therefore, a
relay operation is one half of a cycle.
Pickup value (voltage), specified: As the current or voltage on an unoperated relay is increased, the
value (voltage) at or below which all contacts must function.
Polarized relay: A relay, the operation of which is primarily dependent upon the direction (polarity) of
the energizing current(s) and the resultant magnetic flux. The opposite of neutral relay. Also
called "Polar Relay".
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