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When the box is activated by turning a knob or pulling a hook, a spring-loaded wheel turns, tapping out a pulsed electrical signal corresponding to the box's number. [1] A receiver at fire headquarters announces the alarm through flashing lights or tones, or via a pen recorder, and the box number is matched to a list of box locations. In modern ...
A block and tackle [1] [2] or only tackle [3] is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads.. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and one moves with the load.
An electrical junction box (also known as a "jbox") is an enclosure housing electrical connections. [1] Junction boxes protect the electrical connections from the weather , as well as protecting people from accidental electric shocks .
Many modern fire alarm pull stations are single-action and only require the user to pull down a handle to sound the alarm. Other fire alarm pull stations are dual-action, and as such require the user to perform a second task before pulling down, such as lifting or pushing in a panel on the station or breaking a glass panel with an attached hammer.
Below is a list of NEMA enclosure types; these types are further defined in NEMA 250- Enclosures for Electrical Equipment. Each type specifies characteristics of an enclosure, but not, for example, a specific enclosure size. Note that higher numbers do not include the lower-numbered tests. For example, types 3, 4 and 6 are intended for outdoor ...
Box connectors join conduit to a junction box or other electrical box. A typical box connector is inserted into a knockout in a junction box, with the threaded end then being secured with a ring (called a lock nut ) from within the box, as a bolt would be secured by a nut.
A Class B push–pull output driver using a pair of complementary PNP and NPN bipolar junction transistors configured as emitter followers. A push–pull amplifier is a type of electronic circuit that uses a pair of active devices that alternately supply current to, or absorb current from, a connected load. This kind of amplifier can enhance ...
In electrical distribution, a fuse cutout or cut-out fuse (often referred to as a cutout) is a combination of a fuse and a switch, used in primary overhead feeder lines and taps to protect distribution transformers from current surges and overloads. An overcurrent caused by a fault in the transformer or customer circuit will cause the fuse to ...