Some old test equipment have a 1 MHz frequency reference input.

My BG7TBL GPS Disciplined Oscillator produces a 10 MHz sine wave.

Decade counter.

A 74LS90N can be configured to divide by 10 (/2 and /5) but wants to have a square wave input.

Schmitt Trigger

This circuit has both a high and a low trigger-level on which its output changes from low to high and v.v. thus converting a sine-wave signal to a square wave.

Points of interest.

Switching speed of both the decade counter and Schmitt Trigger.