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English: Pictorial diagram of electric doorbell wiring with a dual-solenoid chime, front door pushbutton switch and back door pushbutton switch. Date 13 November 2013, 20:03:54
Doorbell mechanism from 1884 in Andrássy Avenue, Budapest Antique mechanically operated shop doorbell on a torsion spring. William Murdoch, a Scottish inventor, installed a number of his own innovations in his house, built in Birmingham in 1817; one of these was a loud doorbell, that worked using a piped system of compressed air. [1]
These were single-stroke bells: applying current to an electromagnet pulled the bell's clapper against the bell or gong and gave one chime. The bell did not ring continuously, but only with a single ring, until current was applied again. To sustain the tone, these bells were usually much larger than are used today with interrupter bells.
Knob-and-tube wiring at a museum display. Over time, the price of electrician labor grew faster than the cost of materials. This removed the price advantage of K&T methods, especially since they required time-consuming skillful soldering of in-line splices and junctions, and careful hand-wrapping of connections in layers of insulating tape.
Diagram of a simple electrical cable with three insulated conductors, with IEC colour scheme. About 1950, PVC insulation and jackets were introduced, especially for residential wiring. About the same time, single conductors with a thinner PVC insulation and a thin nylon jacket (e.g. US Type THN, THHN, etc.) became common. [citation needed]
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A circuit diagram (or: wiring diagram, electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations.
A transformer supplying a three-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding has a center tap connected to a grounded neutral. As shown in Fig. 1, either end to center has half the voltage of end-to-end. Fig. 2 illustrates the phasor diagram