nelson@sgi.com (Nelson Bolyard) (05/17/91)
WDBURNS%MTUS5.BITNET (William D. Burns) reposted one of the "busy indicator"
schematics that were posted to comp.dcom.telecom in February. When that
schematic was first posted, I tried to reply to the original author to
discuss it, but my mail bounced. I attempted to analyze this busy indicator
and I concluded that when the line is in the "on hook" state, this circuit
draws much more current from the line than is permitted for an on-hook
line. Also, it seems to me that Q2 ought to limit the current flowing thru
Q3 (by lowering the voltage on the base on Q3) to the point where the LED's
light is imperceptibly bright. Finally, it would seem this circuit would
have bad effects on the signal quality of high speed modems.
Rather than spread my probably-ignorant analysis all over the net, let me
ask that if you are prepared to discuss an analysis of this circuit, and are
willing to take the time to do so, then please reply (via email) to me.
Thanks.
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Nelson Bolyard nelson@sgi.COM {decwrl,sun}!sgi!whizzer!nelson
Disclaimer: Views expressed herein do not represent the views of my employer.
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