[GreenKeys] Parallel to Current Loop Conversion

[Rodger Casey]

I got a real kick out of a 40-pin IC package being described as "old school."  I must be older than I fully realize...  :-)

> On Dec 4, 2014, at 7:55 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:
> 
>> On Thu, 4 Dec 2014, Cory Heisterkamp wrote:
>> 
>> Before I go and reinvent the wheel, I was wondering if anyone had a proven
>> old school circuit (no micros) for converting parallel 8-bit data to
>> ASR-33/35 friendly 110 baud equivalent. This won't be a computer interface,
>> rather the parallel source will either be switches or relays with an
>> additional line to 'release' the data when ready.
> If it's a Model 33 that's involved, note that the keyboard and tape reader
> contacts are open when they are not transmitting, so you can connect your
> relay-contact parallel signal to the M33 distributor and then kick it
> off when you are ready to send a character.  This is the way it was done
> in the console terminal for the Burroughs B5500 computer, if I remember
> correctly.