Mechanical switches come in a variety of types. A glance through a catalogue will reveal many – but the principle for them all remains the same –
joining wires in a mechanical way by :
moving a slider or lever
using an electric coil to magnetise a contact
switching by electronic means using a voltage divider and sensor
A simple switch can be a ‘push-button’ type.
This can ‘lock-on’ or it can be a ‘push-to-make’ or a ‘push-to-break’ action.
All of these actions give a DEFINITE – ON or OFF signal and they could therefore be called ‘digital’ switches. If there is some in-between state possible – as in a volume control of a radio – then the switch could be described as an analogue switch.
Switches like this can also be operated by a ‘toggle’
or slider action.
Although the second three contact points can’t be seen on this small sketch they could be present alongside the set we can see. This would make this a DPDT switch. If the contacts we can see in the sketch were the only ones on the switch, then it would be of the SPDT type.
A supply wire joined to the centre of the switch shown here could be made to link to a part of the circuit connected to the left contact or a part
It is easy to see what a Double pole – Double throw (DPDT) would look like –
or a double pole – single throw. (DPST). Just be checking if there can be two ways or only one way for the contact to be made. These kinds can be in Push-to-make and push-to-break too.
If only one set of contacts is available on the back then the switch is said to be
Single Throw - SPST
Two ways for the contact to be made .....
Centre to left or centre to right.
Think about theses switches -TV controls, webcamera, keyboard and monitor switch. What kinds of switches have been used for them ?
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