A magnetic pickup is an AC generator.
It is normally installed into the flywheel housing of an internal combustion engine, so that the starter ring gear acts upon it to generate a voltage pulse each time a gear tooth passes the end of the sensor.
FW Murphy MPU Magnetic Pick-up
MP3298: Type 300 Stainless Steel. Locknut: Type 300 Stainless Steel. MP7905 and MP7906: Type 6061 Aluminum/Anodize Class 1. Locknut: Steel Nickel Plated.
Output Leads (all models):
Two insulated leads, 20AWG, STR/TEF insulated per MIL-W-16878D Type E, 1 White and 1 Black.
Output Voltage (all models):
200 V.P.P. TYP. (tested at 1000 I.P.S. 20 Pitch gear, 0.005 Gap., and 100K OHM Load).