TRS-80 curiosity

Fred Cisin cisin at
Fri Apr 14 10:15:44 CDT 2017

On Fri, 14 Apr 2017, Peter Cetinski via cctalk wrote:
> The EI expansion port was originally called the Screen Printer port 
> because that was the only accessory that connected directly to the 
> TRS-80 bus.


Later, the Voice Output device (repackaged Votrax?) used the bus 
Later, the Voice Input device used the bus connector.

After we (Elcompco) built a 4 port "Bus Extender" (with active 
termination), we found that the Voice Input device had a hidden 
undocumented pass-through of the bus.  All essential to connecting an X-10 
interface and being able to say, "LET THERE BE LIGHT!", with a response of 
X-10 "all lights ON", and a voice responce of "BY YOUR COMMAND".  Thus 
demonstrating the level of practical applicability of a home computer.

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