The signal from the distributor or ignition box(EDIS) to the ECU. The ECU feeds back what the timing advance should be to the TFI or EDIS. Google it! You might want to search "ford pip"
Another way of looking at it is that it relays cylinder-displacement to the computer; it tells the puter which cylinder will be needing spark and injector pulse.
It's called a stator in most parts if you need to buy one.
The primary function of the TFI-IV ignition system universal distributor is to direct the high secondary voltage to the spark plugs. In addition, it supplies crankshaft position and frequency information to the ECA using a Profile Ignition Pickup (PIP) sensor in place of the magnetic pickup or the crankshaft position sensor used on other models. This distributor does not have any mechanical or vacuum advance. The universal distributor assembly is adjustable for resetting base timing, if required, by disconnecting the SPOUT connector.
The PIP replaces the crankshaft position sensor found on other EEC-IV models.
The PIP sensor has an armature with four windows and four metal tabs that rotate past the stator assembly (Hall-effect switch). When a metal tab enters the stator assembly, a positive signal is sent to the ECA , indicating the 10°BTDC crankshaft position. The ECA calculates the precise time to energize the spark output signal to the TFI module. When the TFI module receives the spark output signal, it shuts off the coil primary current and the collapsing field energizes the secondary output.