0A5 Voltage Regulator Tube – Cold-Cathode Gas Regulator

The 0A5 is a cold-cathode, gas-filled voltage regulator tube — the "0" prefix marks it as needing no heater, since it conducts through gas ionization rather than thermionic emission.

• Tube type: Cold-cathode gas voltage regulator
• Base: 7-pin miniature
• Heater: None (cold-cathode, gas-ionization type)
• Typical use: Voltage reference/regulation in vintage radio and instrument power supplies

Part of the 7-pin miniature-base regulator family alongside 0A2, 0B2, and 0C2.