Re: data diodes

From: Douglas W. Jones <jones_at_cs_dot_uiowa_dot_edu>
Date: Mon Dec 04 2006 - 10:12:01 CST

On Dec 2, 2006, at 5:10 PM, Charlie Strauss wrote:

> Alas, optoelectronics is not so simple. HP and others make things
> that look like LEDs that contain both an emitter and a detector. So
> one is not home free pointing to an LED and saying well that only
> emitts but does not get a signal back.

This is why the device, in its context, is so very important. Indeed,
even conventional LEDs work as (lousy) photocells, so you can design
circuits that use them to receive signals. So, the entire context of
the device matters. If you connect a device that resembles an LED to
a big black epoxy brick, you don't do a good job of convincing me what
it does. If, on the other hand, it's connected through diodes and
resistors to an RS-232 serial port, you might convince me that it's
an output only device.

> I think the four wire vactrols are quite convincingly unidirectional.

Only if you know what's inside the epoxy case.

                Doug Jones

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Received on Sun Dec 31 23:17:05 2006

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