SG-4S is a voltage regulator tube. Equivalent to the 0D3, VR150/30.
Name: SG-4S;
Type: Gas stabilizer;
Cathode type: cold;
Filling: argon-helium;
Envelope: glass;
Ignition voltage, V: 180;
Stabilized voltage, V: 145-162;
Current, mA: 5,0-30;
Voltage recurrence, V: 0,5;
Ready time: 3.