The SENSOR ON the MTH-90 Very simple lamp sensor

Very simple circuit on the Thyratron light - sensor switching.

https://youtu.be/rNeGtIFzj_4

The glow discharge tiratron MTH-90 has a non-axial cathode, anode and one grid (the ignition moment of the discharge is controlled by the grid current). Used in devices of automatics and telemechanics, metering devices, metering, communications and other electronic equipment for converting electrical signals of low power and as an ion relay and photocell in the sensing devices and the indicators of radioactivity. 

A SIMPLE STROBE on mtkh-90 https://youtu.be/xaOyFBn_kl4

Reflex generator https://youtu.be/C6rwindxPII