Magnetic Amplifier circuitry, these controls were almost impervious to lightning. Not super precision, no advanced features. but very rugged! We have serviced these for years, and know how to return to you a control that will last another 10+ years (or at least as long as the regulator it’s hanging on!)
For more information, please give us a call at 800-330-5409, or email info@shewmakerelectronics.com!