telephone set; telephone device
Refers specifically to the physical telephone apparatus, as opposed to a phone call (電話) or a smartphone (スマホ). Common in technical or formal contexts.
I bought a new telephone set.
This telephone set comes with two cordless handsets.
We installed a new telephone set at the office reception.
The office's telephone broke down, so we called for a repair.
I picked up the telephone's receiver and dialed the number.