how many contacts does a Power SPST switch have to have?

hi i have a couple of Power switches that are SPST and some of them have 3 contacts, some have 4 contacts and some have only 2. which one do i need and which one will work best? please let me know.

All of them will work.

An spst has two contacts. An spdt has three, a dpst has four.

All you need is a pair of contacts which open and close when you want them on or off. The contacts should be rated over the AC voltage you are going to subject them to, and at a current in excess of the inrush for the device.

Keith

so i want the one that just has 2 contacts right?

this one has 3 contacts and they say it is an on/off switch.

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That's a different thing, -think about it for a minute: that's a switch and a light bulb sharing the same housing. Two contacts are for the switch and they join together when the switch is on. The lightbulb is also connected to the "on/off" leg of the switch, so that it too switches on and off with whatever you wire from the switch. However, the (usually neon) light bulb has a second wire coming from it that has to go the Neutral leg of the power, hence a third terminal.

Keith

If you have an illuminated switch, you might as well go for a 2 pole switch (4 contacts). Wiring is _easier_ than 1 pole with lamp, and the switch will cut both connections when turned off. (Great benefit here, where you never know which one is live and which one is neutral.)

JH.