KEY SWITCH for control panels.

Hi guys,
I have to purchase Key Switches for my control panels. The control panel is a very basic one containing a OMRON CPM1A PLC a 24V DC Power supply, and a Safety Relay for Light Curtain. I don't know what type of Key Switch I have to use. But for the operation I want the Key to be removed both in the ON position and in the OFF position. Please help me out cos there are all kinds like Single Pole Sngle Throw, Double Pole Double Throw and all that. If someone could be kind enough to explain me I will be very thankful.
Bye,
Balaji

Single pole single throw just means it has one contact set to use
Double pole double throw means it has 2 contact sets to use
Each contact set has a N.O. and N.C. position/connection.

Determine how many connections you may need then look for your need of removable key in on/off position. The best way to go is find a key switch that you can add/remove/replace the contacts on, then you can configure the switch the way you need it. Talk to your electrical distributors on what they have available.

Thanks, I guess I will foolow your idea and go buy key switches where I can add/remove/replace contacts and then configure the way I want. And I understand that I have to do a lot more reading before going to use C200H but I am quite successfully using CPM1A cos it doesnt have any I/O rack.
Bye,
Balaji