The AT-30 Tachometer is a rugged instrument with solid-state circuitry for indication of engine RPM. This model will accept all signal sources: alternator, magnetic pickup or ignition, and has improved the calibration procedure to a single push button on the back. 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.