The use of the trainer switch as a select or fire button is optional. There are three wires on the trainer switch. The voltmeter or continuity tester is used to find the two wires that have continuity when the trainer switch is pressed. The remaining wire is unneeded and can be removed. Of the two remaining wires, connect one to ground (pin #4) and the other to ``Button 1'' (pin #2). These connections should be taped to avoid having them touch a +5 volt wire.