Here's some additional telephone trivia from the movie.
I took another look at the movie. While in some scenes they made a point of carefully dialing all digits necessary, even ten digits for toll calls, in other scenes they "spun the dial quickly" and dialed few digits to make a call to save screen time.
They made extensive use of keysets (the six button kind) in the newsroom. All were black rotary. The line lamps lit up appropriately. Sometimes several people listened in to a conversation, and they showed Bernstein unscrewing the transmitter so that the other party wouldn't notice the listening in. They also correctly used the intercom button (far right) on the keyset for newsroom floor calls.
One error, very common in movies _to this day_ was Redford using a single slot pay phone and the ding-ding sound when his coins dropped. Single slot pay phones eliminated that sound, but that's still heard today in productions.
Redford used a phone booth which of course nowadays is a rarity. This booth was metal with a semi-modern sign on top. It had the old Bell System logo, but the word "phone" spelled out in lowercase letters in a modern style. It was a rotary single slot, with a red+white instruction code, which suggested the phone was equipped for TSP/TSPS and possibly 911. (Was basic 911 service available in 1972?)
Almost everybody in the newsroom had a manual typewriter. These were large office grade and relatively modern machines for their day. They seemed to favor Olympia brand. Redford had an old tiny portable at home.
There was a large fax machine in which they got a copy of another newspaper.
In one scene they search through call slips at the Library of Congress. Today this could be done by computer instantly. In the old days, library books had a card in the back which was removed when someone checked out the book, and they wrote their name on that card. Some places used a code number instead of a name. But looking at the card would say who had the book before.
In another scene Redford is on the floor searching through a pile of city phone books to find out about some person. Obviously today that would take but a second through the Internet and they'd get a lot more information about someone. For example, if someone was active in sports or in clubs, often there is a web reference to that activity, which could tell where someone went to school, etc.
I was surprised at how freely people spoke to the reporters considering they were ordered not to and knew they were sitting on hot stuff that could come back and bite them on their butts. When I watch cop dramas, I'm surprised how much people tell cops without first calling their lawyer or just keeping their mouth shut. Cops have a way of intimidating people by their badge. But newspaper reporters have no badge, no authority.
If a reporter asked me questions about myself or my employer I would never say a damn thing. They are not your friend "trying to help you" anymore than a cop is who says the same thing. I remember when the film "Absence of Malice" came out journalists were very offended but that movie was accurate in how journalists can be sloppy and hurt innocent people as a result.
If I recall, W&B's efforts changed the face of political journalism into a more aggressive role. At that time they became big folk heros and lots of kids chose to study journalism as a result, causing a glut in the field. (Even then newspapers were shrinking with people getting laid off.)
What is forgotten about Watergate is that a lot of young innocent people got dragged down and ruined by careless reporting or guilt by association. It is one thing to get the guilty, but our quest isn't so high and mighty that it's ok to sacrifice the innocent too along the way.