Mechanical device and Pickup arm

Mechanical device noun - Mechanism consisting of a device that works on mechanical principles.

Pickup arm and mechanical device are semantically related. In some cases you can replace phrase "Pickup arm" with "Mechanical device", this phrases are similar.

Pickup arm noun - Mechanical device consisting of a light balanced arm that carries the cartridge.

Mechanical device and pickup arm are semantically related. You can use "Mechanical device" instead a noun phrase "Pickup arm".