There was extensive research that went on before they built one of the earliest digital computers, the ENIAC.
They already knew that it was going to be very large and have a whole hell of a lot of wiring, so before they even started building it, they studied which sorts of wiring insulation rats liked the absolute least.
It turned out that rats and mice can hear the electricity going through the wires, and it bothers them to the point they chew the wires to try to stop the sounds they hear, so the types of insulation that also insulate those frequencies also help repel the rats/mice in general.
There was extensive research that went on before they built one of the earliest digital computers, the ENIAC.
They already knew that it was going to be very large and have a whole hell of a lot of wiring, so before they even started building it, they studied which sorts of wiring insulation rats liked the absolute least.
It turned out that rats and mice can hear the electricity going through the wires, and it bothers them to the point they chew the wires to try to stop the sounds they hear, so the types of insulation that also insulate those frequencies also help repel the rats/mice in general.