when current is being conducted through the field winding the signal which causes the field winding to conduct current is called field switching and the signal which monitors this pin to determine the average field current is called field sense w 3 neg in represents the ground reference for all voltage measurements w 4 phase in represents the alternating current sense signal that is provided by one of the alternator stator windings w before rectification this signal is called ac sense and it comes alive whenever the field winding is energized and the alternator shaft is turning the signal is processed in the rpm buffer so that the signal frequency reliably indicates the alternator 39 s shaft speed w 5 eng in represents the energize signal which is operated to bring the regulator into operation and to initialize the micro controller it is also called the energize signal this signal is typically derived from the battery and passes through a variety of control switches before it arrives at the designated regulator pin in some applications alternator operation is self energized and the energize signal is generated after the alternator shaft begins turning in such cases this signal is internal to the alternator and regulator circuit and no external signal is supplied average field switching this circuit produces a voltage proportional to the time within a period that the field coil is conducting current e g duty cycle temperature sense this is an analog voltage proportional to the ambient temperature as measured by a temperature sensor included for the sake of.