Well, there are two types of insert jacks. There is the single-point, unbalanced insert, which is usually standardized as tip=
send, ring=
return,
shield=common, and then there are dual-point inserts, with separate balance
send and
return.
I imagine you're using a
console with single-point, in which case I'll sum up what the previous posters have mentioned. You want a normally-closed (NC) footswitch, and you want to rewire it with a
TRS connector (it normally has a TS
connector) so that the
switch is going between the tip and ring. When you press it, this connection opens, breaking the signal.
If you get a switchable footswitch (which has a slider on the bottom to choose between NO (normally open) and NC operation, you can also
switch it to be NO, in which case it becomes a push-to-talk.
On a dual-point insert, your best bet would be to
wire a box with a TS
jack for the footswitch, and a balanced out and in to connect to the
console's insert jacks. The insert in/out are connected straight through, and the
jack for the footswitch gets wired in parallel, with the tip wired to pin 2 of one of the XLRs, and the sleeve to pin 3. In this case, you want a NO
switch; pressing the
switch will short pins 2 and 3 together, effectively muting them (this is how
mute switches in most switchable
dynamic mics work).
HTH,
Andy