rewiring double light switch

[wmc]

Hi - I want to replace a double light switch. The new switch has COM, L1, L2 connections in two separate blocks. The old switch has the same, and for one block there are wires in all three, for the other block there is only COM and L1. I tried to replace with the new switch using the same wiring pattern but it trips the electric fuses, I put the old switch back on and all works fine. Have I done something stupid or is the switch faulty?
Similarly, I want to replace a single light switch, it only has two wires and two connections on the switch itself, how do I wire up a new switch with three connections?
Many thanks

 

[EFLImpudence]

The old switch has the same, and for one block there are wires in all three,

That is because there must be another switch which operates the same light.

I tried to replace with the new switch using the same wiring pattern but it trips the electric fuses, I put the old switch back on and all works fine. Have I done something stupid or is the switch faulty?

Either way it should not have caused a trip.
Did you perhaps pinch a wire when screwing back the switch?

Similarly, I want to replace a single light switch, it only has two wires and two connections on the switch itself, how do I wire up a new switch with three connections?

Clue:

for the other block there is only COM and L1.

 

[Taylortwocities]

The two switches are probably laid out differently.
Post a photo of the old one (still connected)
And the new one and we will try and guide you.