Frequencies: 4 or 40 hertz (cycles per second) selectable by switch

Waveshape: pure square wave AC

Maximum voltage output: 18 volt source

Current detector: red light comes on with at least .19 milliamps (190 microamps) output

Current control: manual rotary control (250K potentiometer)

Maximum current output: .44mA on both wrists

Battery voltage detection: if voltage is sufficient and circuitry is working correctly then the current detect light will come on with electrodes connected to the user 

Power source: two replaceable 9 volt batteries