2N4427 - Silicon planar epitaxial overlay transistors
NPN overlay transistors in TO-39 metal packages with the collector connected to the case.
The devices are primarily intended for class-A, B or C amplifiers, frequency multiplier and oscillator circuits.
PINNING - TO-39/1 PIN 1 2 3 emitter base collector handbook, halfpage 2N3866; 2N4427 APPLICATION