Get on the Horn

Usually used when people want to call someone on the phone. Wondering if anyone had any idea about its origin.

The horn is the phone. For example, people also say "I'm on the horn" during a call. I'm guessing that this nickname came from the shape of early receivers, which were roughly cylindrical with one flared end.

I believe that the horn refers to the device used on ships
to contact the engine room from the bridge. This was an actual
tube with both ends flared(like a horn). The term is still used on ships
today.