That's how I used to transfer files to my coding buddies.
On the phone, hex dump in S-record format, then read out loud while the other side would type in the line. Checksum matches? Next line...
Our respective parents were not too happy about this unplanned usage of their phone lines but it saved a ton of cycling.
That's how you do it! What's the today's equivalent that kids do?
I ended up typing it in 1k at a time, and independently typing in a CRC32 utility to check that I'd done it properly.
(That was to install Windows 98 on a computer with no drives, if I recall. So, not so very long ago.)