184
The Tektronix Type 184 is a compact, solid-state, crystal-controlled time mark generator. The generator produces push-button selectable time marker intervals from 2 nanoseconds to 5 seconds. There are also seven push-button selectable trigger pulse rates from 1 microsecond to 5 seconds.
The 184 contains a 10MHz crystal in a 75C oven. The frequency is specified to be within 0.001% of 10MHz at ambient temperatures between 20C and 30C. In the same temperature range, the frequency is specified to vary less than 3ppm (30Hz).