Most people will have a used a power strip with a surge protector at some point - this will shut off an electrical current when the power becomes too high.
If you are setting up audio-visual equipment in a courtroom or other building with an older electrical system it may be wise to also use a line (or power) conditioner which will control the voltage which hardware receives. More modern electrical systems will have line conditioners built-in, but many older facilities will lack them.
Low voltage dips will put stress on electrical devices and cause them to fail. A line conditioner will keep the voltage with a safe range.
A typical line conditioner will look like this model:
The power cords from multiple laptops, printers, and other devices can be plugged into the line conditioner, and the line conditioner's power cord will be plugged to a wall outlet.
The line conditioner should have warning lights which indicate when the power is too high or too low.