[GreenKeys] An advanced approach to driving a 60mA Teletype from a USB port

[John Nagle]

> John -
> 
>   You mention:
>> If you model the
>> standard "120V supply through a 10K resistor" approach to driving a Model
>> 15
>   Common 60mA loops use a 120 VDC supply through a 2k Ohm dropping 
> resistor.  1/5 the resistance provides 5x the di/dt of your 10k loop 
> resistance.
> 
> Dave Ross    N7EPI

    Right; in fact I use a 2K 10W resistor in my own classical design at

http://www.aetherltd.com/connecting.html

See R7.

    Over 90% of the energy in classical designs goes into heating up
the ballast resistor.

					John Nagle