The MDE2-16 magnetic encoder from Micro-Drives, Clearwater, Fla. (www.micro-drives.com), measures only 8.4 mm long and 16 mm in diameter. It provides two-channel TTL output with 16 counts/rev resolution. They are powered by voltages between 3.3. and 26.5 Vdc and are reverse-voltage protected and output-current limited. They operate in temperatures from -40 to 302°F. The encoder is available on several miniature dc motors from the company and can be coupled with planetary and spur gearheads to build a complete motion-control solution.