Print clock face , install a clock movement.

use a standard Clock movement , Size : 56mm x 56mm , but Clock movements of different sizes can also be installed.

Probably only radio operators, amateur radio stations, understand what this is.

In telecommunications, radio silence or emissions control (EMCON) is a status in which all fixed or mobile radio stations in an area are asked to stop transmitting for safety or security reasons.

The term "radio station" may include anything capable of transmitting a radio signal. A single ship, aircraft, or spacecraft, or a group of them, may also maintain radio silence.