The CT-15+ is an audio output triode with a 2.0 V filament. The anode voltage range is 60-120 Volts.
It was in 1926 that Cleartron introduced their plus range of audio output valves.
The silvering of the envelope obscures the electrodes. Etched into the glass is the Type designation CT15+ with the plus looking like an X, the CT logo and 2 Volts.
The balloon envelope is 40 mm in diameter, and excluding the B4 base pins is 98 mm tall.
References: 1003 & 1043. Type CT-15+ was first introduced in 1926.
Absolute Maximum Operating Conditions¶
Updated May 16, 2019. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f