I remember the "Modem 2B" from a few sites I had to deal with in the very-early-80s. Horrible things that often needed you to make 10 calls before it synced with the remote-end, and then only 300 Baud! Which when you're online for 10 hours a day paying long-distance phone charges ran up some horrid bills!
I was happy to get them slung out and replaced by EPS8/EPS25 circuits with EMI/SE-Labs '9620" modems - giving us permanent 9600-Baud intersite links.
On dialup we also had a bunch of the wood-cased acoustic couplers as mentioned above - from memory they were made by "Andersen Jacobson" - and at one time I was happy to sign-off £2500-a-time for Texas Instruments "Silent-700" data-terminals [Keyboard, thermal printer, optional 1 or 2 cassette drives] - these were used for offline data-preparation, recording the keystrokes on to one of two cassette-drives [the second one allowed for local editing] before you did the dialup-and-acoustic-coupler shimmy to upload your afternoon's efforts to Head Office]
http://www.computinghistory.org.uk/u...duct-90649.jpg