Gaps in the collection (was Re: rarest computers. )

[Vassilis Prevelakis]

ard at p850ug1.demon.co.uk (Tony Duell) wrote:
> Talking of HP using 555 timers, they used one to drive the power-on light 
> in the HP86 (and I assuem the HP97). [...]
(nitpicking here, you are talking about the 87)

> So the LED is dark if the machine is off, on steadily if the machine is 
> on and no error (555 is held reset, so the output is low all the time), 
> and blinks (controlled by the 555) if there's an error. 

Actually the LED blinks when the machine is busy (e.g. running a program).
This is very neat as with the HP85 you sometimes do not know whether the
program has finished or is still running.

**vp