timer delay swtching

[AnonymousImport]

am trying to install pneumatic time delay switches on staircase feeding one pendant from two points. the switches have 3 terminals.
common - normally open - normally closed. how do they replace the common -L1 - L2 terminals of a standard 2 way switch.

 

[AnonymousImport]

A single throw switch L1,L2 simply breaks or makes the circuit, a double throw transfers the live (common) to either the normally open (equivalent of off) or normally closed (equivalent of on) terminal. In a two way switching circuit, lets call the two switches upstairs and downstairs (u and d for short!) the live feed is connected to the common of the u switch and the light is connected to the common of the d switch. The normally open of u is connected to normally closed of d and vice versa. So either switch can break or make the circuit, irrespective of the position of the other switch. Try drawing it out on paper and you'll see how it works!