I was working on an install late last week with a URC MX-850 controlling the gear via an MRF-300 in the rack - two of the a/v components had IR input jacks in the rear panel (Parasound NC7100 and Motorola 3412 cable box), so I was looking forward to useing these rather than emitters ... wired up a mono 3.5mm jack from the MRF300 to each component, yet *none* of the remote commands sent from the MX remote affected the components??

Replacing the direct IR jack with an emitter-type cable (connected to the same MRF port, natch) _did_ control the relevant component, though.

Am I missing something? Why shouldn't the mono-type direct IR cable work? The only hint I have is that the NC7100 docs contain the admonishment...

The 7100 IR inputs require an “amplified IR block” which are accessories for IR repeater systems

However, I'd think that the MRF-300 meets this requirement, since it's effectively recreating the IR signal from scratch (rather than "reflecting" it, as with a passive IR repeater system). Any ideas why the 3.5mm direct IR cables didn't work??

I know this is a really obvious question, but I'll ask it anyway, as you didn't state you did these things:

Did you read the Manual on the MRF-300?
Did you check for interference?
Did you change the channel on the MRF to other than 0?
Did you try adjusting the line level output?
Did you try sending commands to only 1 line level output?
Did you try disabling the front IR blaster?

If you haven't tried any or all of the above, download or find your instructions, and try all of these in the order given in the manual. I find this process makes this item work!

Yep, I did indeed perform all of the above steps ... no interference, the RF signal from MX was coming thru w/o issue (as shown by both the antenna & MRF's led); channel was set to "B"; line level adjustment didn't at all affect the direct 3.5mm cable's not working; the remote was configured so that each component's IR commands were only sent to the MRF port to which it was connected, and of course the front IR blaster was disabled ;)

There is always the possibility that these jacks, even though they are there, don't work. Our SA cable boxes have an IR in jack, but they don't work (or at least SA doesn't tell us if we have to do something special to make them work). The LG TVs we use have an IR in jack, but I recently found out in order to use them, there is a small circuit you need to build to interface standard IR to this jack (another project I will have to work on when things slow down).

Don't rule out the fact that these may not be standard IR jacks, they may use some sort of de-modulated IR (like Sony S-Link) or instead of resting low and pulling up for signal, maybe they rest high and need to be pulled low. Most of the things we use Integra, B&K, Sony can all be hardwired but there are a few non-standard things out there.

The 3.5 jack on the Motorola is for an IR emitter output of the cable box to control a VCR. UR out of luck for a non emitter install.

Just a silly sounding curiosity.... Did you check continuity and polarity on the plugs?

"The 7100 IR inputs require an “amplified IR block” which are accessories for IR repeater systems"

Net, this means that the 7100 will not power up an IR receiver, it will still receive Sig/Gnd.
Not sure what your problem is, iI have run IR direct into the Parasound products with no problems.

Each local cable company decides whether or not to turn on the features of the boxes they get from Scientific Atlanta or MOT. So Comcast in San Francisco may use some features of the 7100 while LA utlizes different ones or none at all. So you may find issues in one part of the country which do not pertain to other parts. There are also multiple manufacture runs which mean that even 2 - 7100s in a market may not have the same feature set.

As mentioned above, the IR jacks on cable boxes are outputs to control VCRs. I've had little luck connecting the MRF to devices as well. It has to do with the fact that the MRF only has a 9V IR signal where most components require 12V.

If this is true... would not an amplified block cure this issue?

I use RTI so I don't have these issues....

An RP-6 would do serial to the NC7100.

Ach, that 'splains it ... I was pretty d*mn surprised to see a 3.5mm jack labeled "IR" on the back of the dct3412 - should've figured it was too good to be true!

didn't check continuity/polarity, but I did try swapping several different cables.

Yah, I was really suprised/bummed that the 7100 didn't work, I'd have thought this should work w/o issue. Guess I'll call Parasound tech and see if I can figure out what happened.

Net:
Give me a call.

Do you have The device set to RF only?
I recall, that Parasound does not like to see IR in the front if you are using the port in the back.