[GreenKeys] Powering a Model 15 currentl loop from a 5VDC 250mApower supply - theory

[Duncan M. Brown]

>
>     My goal was to run a Teletype from a USB laptop without much
> extra gear.  Multiple machines would go on multiple USB ports.
>

If you want to run a TTY from a laptop, the simplest way is to find
yourself a Mite teleprinter (AN/TGC-14 or AN/UGC-38, -40, -41).  They have
a low-level mode which only requires a few ma. of loop current.  The Mite
will interface to a computer serial port with only a small signal diode (to
convert the bi-polar serial port output to uni-polar).

You do need a computer with a serial port.  Most USB-to-serial adaptors
won't work as they will not go slow enough for TTY.

Have fun,

Duncan, 
  K2OEQ