----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <cctalk_at_classiccmp.org>
Sent: Saturday, September 04, 2004 12:13 AM
Subject: Re: LTC Spec question
> >
> >
> > W/out having the docs to hand, I would like to know the actual
> > electrical specification for the LTC line as implemented in LSI-11 -type
> > systems... what is the backplane (and hence the CPU, etc) expecting?
>
> I've looked at the PSU schemmatics for my MINC, which should be close
> enough...
>
> >
> > Waveform type? Freq range? Levels? If pulses, TTL? CMOS? Duty cycle?
Rep
> > rate?
>
> Waveform : Square wave
>
> Frequency : Mains frequency (50Hz or 60Hz), duty cycle doesn't seem to
> matter.
>
> Open collector driver (pulled up in the bus terminator to +5V)
>
>
> >
> > I need to simulate the incoming LTC signal for a system that will not
be
> > mains powered.... in the older 11/xx systems, this was derived from one
of
> > the windings of the power supply transformer, then made into
> > line-freq-rate pulses by the using module.
>
> That's how it's done in the MINC (and in the LSI11/03 prints I looked at
> which show the H780 PSU). The Minc uses one section of a 339 comparator
> chip connected to the secondary of a mains transformer through a suitable
> resistor netowrk.
>
> >
> >
> > I'm planning on using a small naptha-burning steam engine driving a
> > modified Wimshurst static generator, and then using a calibrated
spark-gap
>
> I always prefered the catostatic.
>
> [OK, a joke. I have a book on making electrostatic generators and one of
> them is called the catostatic. As you may have guessed by now, this
> involves stroking your cat and collecting the accumulated charge in a
> Leyden jar... Knowing my cat, he'd probably get rather fed up with the
> whole idea...]
>
> -tony
>
I rather like old Lord Kelvin's dripping water e/s generator myself - really
has an impact when demonstrated to children - electric charge from dripping
water.
Geoff.
Received on Sun Sep 05 2004 - 18:17:16 BST