The unique SPSR (Self-Powered Sensor) with internal rechargeable batteries provides the required power to any one of (4) Monarch Sensors (see below). The TTL compatible output is switch selectable as either positive going 0-5 V pulses or negative going 5-0 V pulses provided on a BNC connector. The internal rechargeable batteries provide 40 hours of operation between charges. For continuous operation, the SPSR can be powered by 115/230 V ac. Self-powered sensors are a critical element for providing one pulse per revolution for vibration analyzers, spectrum analyzers, stroboscopes, data acquisition equipment, tachometers, balancers, waveform analyzers, and magnetic tape recorders.