The problem and its solution
So the problem is quite obvious – in almost all cases there are more users than copies of the same device which means that some sort of queuing or scheduling is required.
In many cases, each piece of shared equipment or device has a person who is responsible for its maintenance and user guidance. However, in many cases the device resides outside of their lab, and he/she has a hard time monitoring users and correct usage of the device. Thus it is common that shared devices have a calendar listing users’ schedule for work on the device. This is a practical and low cost solution that serves well though it has its own weaknesses, mainly in regard to user monitoring.
For one thing, people tend to be lazy to register for the device, even if it is just fifty feet away from their lab. This of course leads to the device being taken by another user or worse, being used without any knowledge as to who used the device previously (in case of a technical problem, misuse or sullying). Moreover, when it comes to periodic maintenance it can be practically impossible to assess the working hours the machine has been through if there is no counter. Another important issue is user registration: when the device has a paper calendar anyone can reserve a time and start using the device, even if he/she has never received any formal guidance.