Morning guys, stupid question I’m sure, on my old Tig, and I’m talking 18 year old machine, I’m going to. Put a foot pedal on, which I’s fine,but when i was looking at the machine to check connection type i noticed this (attached pic) can someone tell me what its for, instructions have long since g...

Morning guys, stupid question I’m sure, on my old Tig, and I’m talking 18 year old machine, I’m going to. Put a foot pedal on, which I’s fine,but when i was looking at the machine to check connection type i noticed this (attached pic) can someone tell me what its for, instructions have long since g...