The wide-band regenerative receiver used an RCA 955 acorn triode.

The receiver of the initial Zenit system was not sufficiently sensitive, and was redesigned by Truten using a 955 acorn triode from RCA.

This was a superheterodyne unit initially using a tunable magnetron as the local oscillator, but this lacked stability and was replaced with a circuit using an RCA type 955 acorn triode.

The transmitter was increased in power, the antennas had selsens added to allow them to track, and the receiver sensitivity was improved by using an RCA 955 acorn triode as the local oscillator.