These are "as-built"; components were to hand, there are many better ways to do this.
An example of someone doing it better: http://heepy.net/mediawiki/index.php/Optocouplers_for_teletype_current_loop
Current status: untested, not sure it works.
Alternative designs would include:
- Off-the-shelf RS232 convertor, then level-conversion for RS232 to microcontroller. For example the B&B series.
- Solid-state relays instead of low-voltage optoisolators. Essential when driving older teletype machines on 60mA/120V current loop. See for example: http://www.aetherltd.com/connecting.html.