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In the UK, putting 13-ampere BS 1363 sockets on a lighting circuit is discouraged (although not outright prohibited), but 2-ampere or 5-ampere BS 546 outlets are often put on lighting circuits to allow control of free-standing lamps from the room's light switches. In North American site-built and mobile homes, often living rooms and bedrooms ...
Each key of a computer keyboard, for example, is a normally-open "push-to-make" switch. A "push-to-break" (or normally-closed or NC) switch, on the other hand, breaks contact when the button is pressed and makes contact when it is released. An example of a push-to-break switch is a button used to release a door held closed by an electromagnet.
These terminals are usually labelled as normally open, common, and normally closed (NO-C-NC). An alternate notation for Form C is SPDT. [12] These contacts are quite frequently found in electrical switches and relays as the common contact element provides a mechanically economical method of providing a higher contact count. [12]
The internals of a micro switch. Contacts, from left to right, are common, normally open, and normally closed. In one type of microswitch, [4] internally there are two conductive springs. A long flat spring is hinged at one end of the switch (the left, in the photograph) and has electrical contacts on the other.
Figure 4 illustrates a single isolated relay or actuator, in which a single-pole normally open relay controls the voltage source's connection to the lamp. This relay connects one input to one output. An isolated relay can have more than one pole and can have normally closed contacts as well as normally open contacts. Figure 5.
A push switch (button) is a momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated. An automatic mechanism (i.e. a spring ) returns the switch to its default position immediately afterwards, restoring the initial circuit condition.
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5. Electrical devices are shown in their normal conditions. An NC contact would be shown as normally closed, and an NO contact would appear as a normally open device. All contacts associated with a device will change state when the device is energized. Figure 1 shows a typical relay logic diagram.