We had 22 machines at the outset but certainly have less than that at present. Only use them electively if the clear plastic shield is present to protect the settings dials.
Ask your senior to explain how to set up, use and check the system.
A Brief Users Guide
The Full Guide (page 47 starts) - a massive download !
Although this is not our Pacing Box in use, it is a good video to explain the principles of sensitivity, capture and delivery. Only 9 minutes long.