Single conversion general coverage receiver. The S-77A is the AC-DC Marine version of the S-40B and is rarer than the S-40B itself. Its predecessor, the S-52, is the AC-DC version of the S-40. Like the others in the series, this set covers 4 bands from AM broadcast to 44 MHz. It features electrical bandspread, BFO, an RF amp and two stages of IF amplification. Its external appearance is nearly identical and its circuitry is similar to the S-40B with a 25Z5 rectifier and 25L6 audio output substituting for the 5Y3GT and the 6K6GT in the S-40B. The radio's 9 tubes include a plug-in ballast that was selected for either 120 volt or for 240 volt operation. The B- in this set (one side of the power line) is "floating". While safer than directly connecting one side of the line to the chassis, as found in Hallicrafters models such as the S-38 and S-41, an isolation transformer or GFCI outlet (ground-fault circuit interrupter) is recommended for safety. For this radio, I opted to retrofit with an ALCI plug (Appliance Leakage Circuit Interrupter) and cord. The original price was $89.95 in 1952.