Many years of experience were drawn upon in the design and development of these tachometers. Only the best time tested and field proven features were used. These instruments use a three-phase alternating current synchronous motor powered by a remote tach generator. The simplicity of design results in a twofold gain: increased life and reliability and ease of overhaul. A large one-piece frame is a very effective heat sink – a very important feature in drawing heat away from the bearings. All intermediate gears and pointer shafts are suspended on precision jewel bearings. These indicators are qualified for many military applications and have successfully passed temperature, vibration and environmental testing that exceeds most OEM requirements. Housed in a 2 in. diameter hermetically sealed case, Standard ranges for Prop tachometers are 0 – 2000 or 0 – 4000. On the RCA41 percent tachometers the large pointer indicates 0 to 100% over 270° of pointer travel. Small pointer indicates in 1% increments on a 360° dial. Designed for use with a two-pole tach generator conforming to specification MIL-G-9398