Two prong electrical feeler

The pirn used in this mechanism is specially iron coated on the bunch section. When there is enough yarn on the bunch there is no contact between the feeler prong and metal of the pirn. But when there is no yarn in the bunch then the feeler prongs come into contact with the metal portion of the pirn and completed the circuit. The circuit is incomplete until contact is maid across the feeler prongs. This contact is made when the slay is approaching its most forward position and a metal band set into the stem of the pirn adjacent to the butt has been uncovered i.e. yarn is being withdrawn from the bunch. The completed circuit energizes the solenoid so that the magnetized core attracts the trip lever into a post opposite to a suitable driving point which is an oscillating tripper heel and makes a slight rotation of the changing shaft which ultimately activates the change mechanism. Since yarn does not conduct electricity, the circuit is not completed when the metal band is covered with yarn.