Walney wrote:
Will the Denon (which has
the infrared sensor) control the Onkyo?

Unlikely

Would connecting them be
likely to cause any damage?

Possibility of damage, yes.

As an alternative approach, would a "universal" remote be of any use?

Nope. Your cassette deck is blind - it won't see it!

However, some remote control bus systems simply distribute the
demodulated serial stream transmitted from the IR remote around the
addressable internals of the equipment (e.g. RC-5/I2C), others
communicate with a central microprocessor that resends rather more basic
controls signals specific to each peripheral device.

If it's the former - a distributed system, AND the IR carrier frequency
& modulation method is the same for both Denon/Onkyo, AND the bus
addressing is compatible, AND you can get the two boxes to electrically
connect without fireworks than that is a _very_ long shot of working
using the two original IR remotes, or one universal.


I'd be very grateful for any advice.


Someone with a knowledge of hacking with digital control logic,
equipment schematics, a scope and a PIC programmer would be able to sort
this out, but the development time would cost more than the equipment. :-(

--
Adrian C