Deadbolt A bolt operated manually and not actuated by springs. When locked, the bolt connot be forced back. A deadbolt is operated (projected and retracted) by a key cylinder or lever handle.
Deadlatch A latch in which the latchbolt is positively held in the projected position by an auxiliary mechanism.
Decibel (dB) An increment of measurement used to compare measured levels of sound energy (intensity) to the apparent level detected by the human ear, expressed as a logarithmic ratio.
Deenergize To remove power.
Delay A period of time before or during an event.
Delay on break A term used to describe a mode of operation relative to timing devices. The delay begins when the initiate switch is opened (delay break of initiate switch).
Delay on energization A term used to describe operation relative to timing devices. The delay begins when the initiate switch is closed or application of power to the input.
Direct current (DC) Electrical current that travels only in one direction and has negative and positive polarity. It may or may not have an AC ripple component. DC sources that are unfiltered should be referred to as full-wave or half-wave rectified circuits.
Door open time The time that an access control device unlocks an opening for entry, usually programmable.
Door status switch A DSS is a switch used to monitor whether a door is in an opened or closed position.
Double pole, double throw, (DPDT) A term used to describe a switch or relay output contact form (2form C) in which two separate switches operating simultaneously, each with a separate normal closed contract and a common connection. This form is used to make and break two separate circuits.
Dry Contract Metallic points making (closing) or breaking (opening) a circuit. The switch circuit must have its own source of power and is merely routed through the dry contacts.