The AT Series tachometer is a rugged instrument with solid-state circuitry for indication of engine RPM. It is equipped with a ring nut for mounting into a standard 3-3/8 in. (86 mm) dash mounting hole. A full 240° sweep of the pointer gives an accurate indication on a large easy–to–read scale, and the dial can be illuminated for night reading. The ATH Series model is also equipped with hourmeter to record the elapsed running time of an engine.

These instruments are designed to function with Alternator, Magnetic Pickup or Ignition signals from:

• pulses generated by an alternator with 4, 8, 12, 14 or 16 poles on the rotor (3 - 52 PPR);
• pulses obtained from the ring gear of an engine by means of an electromagnetic sensor (magnetic pickup). The instrument is designed to function with flywheels having anywhere from 50 to 300 teeth;
• 2 - 10 cylinder, 4 cycle spark-ignited engines. Not intended for use with Capacitive Discharge (CD) ignitions or magnetos, only for inductive, automotive-type ignitions.

The tachometers are powered by a 12 or 24 volt battery and are reverse polarity protected. These units are for negative ground or isolated electrical systems. They are specially designed for use on truck, marine, industrial or stationary engines.