Here is a fascinating, very well made short feature film from 1937 showing and explaining how images were sent by telephone back in the 1930s. There's even an acoustic coupler: https://www.youtube.com/watch?v=cLUD_NGE370

I actually came across that a few days back. Fascinating time capsule.

Hmm that You Tube clip brings back memories when I first encountered a Picturegram machine whilst based at Wagin in WA's southern wheatbelt when Donald Campbell in his speedboat Bluebird broke his water speed record on Lake Dumbleyung about 50kms east of Wagin.
The West Australian newspaper had reporters and photographer there and they would bring the photos into the Wagin telephone exchange and set their machine up in amongst the equipment racks and we would patch the gear into one of the 6 voice circuits we then had Wagin to Perth and at the Perth end the GPO switchboard would be disconnected from that circuit and the PMG Picturegram machine would be patched onto that Wagin circuit and away it would go.
Used to take quite a while to transmit each photo over the 3.3kHz bandwidth voice circuit and they always looked good in the newspapers next day though.

10 or so years later whilst I was based at Port Hedland after Cyclone Joan trashed the town and again WA News arrived on the scene and because of the distance they did not have their mobile darkroom with them so they used the Battery room at the South Hedland building to develop and print their photos of the destruction Joan had wrought upon the town.
We allowed them to setup their later model Picturegram machine in amongst the gear again and patched them onto one of the many South Hedland to Perth circuits that was until the 4 tube coaxial cable which linked Hedland to the rest of WA was washed away at the Yule River bridge when the river broke its banks.

That created many issues as the only back up Hedland had then was a single 12 Channel system via the inland open wire route back to Perth.
3 of those 12 circuits were taken by the Voice Frequency Telegraph systems so effectively there were only 9 voice circuits available to the traffic being handled by the Manual Assistance telephonists on the top floor of the South Hedland building.

The ABC program came to the local AM transmitter (which we maintained) via 10kHz program attachment that used the bandwidth of 3 voice circuits which via the Coax was no problem but NOT able to be done via the backup inland route so the ABC program was only a 3kHz bandwidth which was from 300hz to 3.3kHz and the ABC were not happy.

The shortage of voice circuits made it difficult to take another voice circuit from the back up route to send pics back to WA News in Perth so the bloke on the ground up there had to accept limited access to send his pics down so he was NOT happy either but nothing else we could do at that time..it was either take it our leave it !!

To make matters even more difficult South Hedland had NO power and our standby plant (35Kva) was fully loaded just running the exchange and limited A/C to the telephonists upstairs.
The rest of the building only had air circulation but NO cooling and with 40C days the place was rather uncomfortable.
The A/C plant had a pair of 30HP compressors to do the cooling and the system only allowed the circulation fan motor to be powered from the standby feed as there was NO Way that a 35Kva plant could start one let alone run a pair of them.

So we all sweated and stank..

QUOTE: there was NO Way that a 35Kva plant could start (Chiller compressor)

That's right, you'd have to look at the LRA (locked-rotor-amps) spec on the compressor first.

Rogue Cop Bullit uses an electromechanical Fax in that late 60s film.

Thoroughly enjoyed that film bringing back memories from my PMG days. (A 1954 TIT).
PMG then Computers was for me a real privilege working as a tech (until computers called me an engineer) when we had to really know, diagnose and repair our equipment and not just go buy another one.