It is not a phone. It never has been.
I used to be a TTY repairman. Back in the days of Ma Bell, a TTY machine (28 KSR) was kept in a vault in a System owned building in NYC. Whenever a President was to stay in town, this machine was “routined” and placed at POTUS’s hotel. It would be connected to some government equipment that was covered by tarps. One of the few NYTel TTY repairman who had been given security clearance was on call 24/7 and would be housed at that hotel for the duration of the President’s visit. Those tarps would NEVER be removed in the repairman’s presence.
SS told us unofficially that his is what, at the time, was known as “The Red Phone”.
Y, this is not to dispute what you posted since this was before Reagan. However, red phones were NOT that difficult to get. All one had to do was pay the monthly charge for it. Many wire rooms on Wall St. had them.
I was an enlisted aide to a Brig Gen and worked out of his house. He had a red phone. The last call I remember was about the B-52s we lost over NVN.
The Red Phones and the Hot Line are two different things. The Red Phones are between US players, and the Hot Line was a comms link between Washington and Moscow.