SWITCHCRAFT 12A NORMALLY-CLOSED JACK
Switchcraft 12A Normally-Closed Jack. Used for Amplifier input jacks and also great for expression pedal option jacks. For example a stompbox volume control could be over-ridden when the expression pedal jack is plugged in, then the expression pedal would control the volume for the pedal. The jack would need to be isolated for this to work (see related products).