I can control tv/vcr/sat ok with the RM-VL710, and now I'd like to control a toshiba air conditioning unit like this one (remote is visible on the page)
[Link: toshiba-aircon.co.uk]

It seems there's some kind of infrared feed-back from toshiba air conditioner to toshiba remote in response to toshiba remote actions, which may confuse the learning process. The RM-VL710 manual says "do the learning into a room where there are no feedbacks", but this way the toshiba remote doesn't work properly, kind of feel orphan.

I only managed once to learn the power-off.

The RM-VL710 lights sequences actually say the learning was completed ok but then it doesn't work. Then RM-VL710 manual says to keep the original remote key pressed until the RM-VL710 acknowledges with special lights sequences, but the toshiba remote doesn't like its buttons to be kept depressed, when you do it sometimes it fires (ony when you release the button) sometime not.
So I tried both keeping original keys pressed, and pressing them just briefly, with no success.

Is there any trick you can share?

I just want to learn:
- poweron
- poweroff
- preset
- temp up and down
nothing more

Thanks.

Is it possible that the air conditioner remote is using an IR frequency that the 710 will not accept?

If you go into another room and teach a command, will the 710 accept it? If it does, will that command work on the A/C?

If the A/C is sending a confirmation signal back to the remote, then when you learn the command you have to stop that confirmation signal from being learned by the 710. From here, and not knowing anything about your A/C, I can only say that you will have to figure out how to do this before you can operate the A/C with the 710.

I'm kind of poking around in the dark here, but I hope I helped a little.

I succeeded in having the RM-VL710 learn all the AC remote commands I wanted.

I'm not sure anymore that there's an infrared feed-back, I think the problem was that I always tried to keep the AC remote buttons depressed until sony acknowledgement like the manual suggested; even when I tried to keep them pressed for a short time as I said in the original post I evidently still unconsciously kept them depressed longer then necessary to 'help' the sony remote learn.

Now I just programmed the sony by clicking on the buttons very quickly, like in normal usage, and then waiting 1 or 2 seconds, w/o doing anything, for the sony to acknowledge them.

Now I'm very satisfied. Certainly the sony lacks the AC remote LCD status, but during normal usage that is almost useless, however there are things that I can do now with a single key press that previously would require 'cycling': there are some keys on the AC remote which work though cycling (ie there's just one key for "fan speed" and you press it many times to get speed1, speed2, ..) but apparently this doesn't not work like for instance sony TV AV1/AV2 where it's the TV which cycles through AV in response to the same IR command; the AC remote actually remembers what it thinks it's the
status of the AC and sends different speed IR commands (even if you use the same remote button) depending on the last used, so I could program on the sony the 5 fan speeds on 5 different keys, and now I can go to the desired fan speed directly, w/o cycling.

All's well that ends well. Happy to hear you have been successful.