Tennelec was a US electronics company founded in the early 1960s by Edward Fairstein in Oak Ridge, Tennessee.
The TC-200 amplifier was a successful early design that established Tennelec as a leader in the nuclear instrumentation field.
Following on the heels of the TC-200 success, the company developed additional components necessary for precise nuclear measurement, including detectors and particle counters.
With the MS-1 and MS-2, the user selected up to 16 frequencies they wanted to monitor by setting them up using binary codes entered via two pushbuttons on the front panel.
Tennelec, still located in Oak Ridge, TN, is now a division of Canberra Industries, which is owned by Areva.