[1] It uses a single AA battery, as its analog electronics require very little voltage.
It was one of the first radios to use the CXA1129 30-pin integrated circuit, which later was responsible for the SRF-39's sensitive and selective performance.
[2][3][1] A variant of the SRF-39, the SRF-39FP, has a transparent case, designed to thwart contraband concealment.
The radio often appears on the commissary lists of U.S. federal prisons, hence the "FP" suffix.
These radios are popular in the DXing community due to their sensitivity, selectivity and ferrite antennas.