[GreenKeys] GreenKeys Digest, Vol 103, Issue 55

[Jim Haynes]

Thanks.  Larry then WA6JYJ and I also built speed converters using
TTL.  Larry's version was written up in Ham Radio, December 1971.

After that came speed converters based on UARTs and also the thing
that was developed for the transmitting side using FIFO chips.  That
allowed you to run the keyboard at 100wpm and transmit at 60 so long
as you didn't fill up the buffer.  As I recall there was an analog
meter that told you the buffer fullness.  That may have been the UT-4.
I guess you could connect it to the tape reader clutch so that it would
stop the tape reader before it overflowed the buffer and then
started again when the buffer got more empty.

An advantage all these things have over gear changing or motor speed
changing is that they can detect a missing stop pulse on input and prevent
the receiving clutch from failing to lock up.  A missed stop pulse can
cause 3 or 4 error characters to be printed, which makes the character
error rate much worse than would be predicted from the bit error rate.
This is especially important in radio work where error characters are
so common.


jhhaynes at earthlink dot net