The Tektronix Type 3B2 is a delaying timebase introduced in 1963 for 560-series scopes except
the 560 and 565. It can trigger on signals up to 30 MHz.
The 3B2 has a 6CW4 Nuvistor triode cathode-follower buffer amplifier at the trigger input, followed by a differential trigger amplifier made of a pair of PNP transistors, with a 2 mA tunnel diode acting as the actual trigger.
The 3B2 has a 1 MHz crystal oscillator and a counter made of discrete transistors.
It generates output pulses that enable it to communicate with a digital unit such as the 6R1 or 6R1A.
The 3B2 uses a 6AL5 tube as the disconnect diode for the sweep.