Also, be aware that teletypes come in two encoding flavors, the so-called "7 level" or the ASCII-speaking one (e.g. model 33) and the "5 level" (e.g. model 35) which uses its own code.
I used an adapter from a S100 CP/M machine to a 5-level international telex machine - the code was called BAUDOT.
The adapter converted RS232 signal from a serial printer port to current loop at standard telephone line voltage. Some driver code converted ASCII text to BAUDOT output. IIRC no handshaking was used. ASCII bit 6 triggered the register shift, I think. I still have the 8-bit 8080 Assembler source for that driver, if OP or anyone else wants to run a 5-level BAUDOT telex machine from a RS232 port. Standard baud rate was 50bps - a bit less than 5 chars per second. The hardware adapter was fairly simple as I recall, but what I have left of it has been robbed of some components over the years and I don't have a schematic.
My setup was output-only. Presumably a reverse adapter for input would be equally simple.