Using the Harmony PS3 Adapter with a Logitech IR Extender

I use the Harmony PS3 adapter along with a Logitech IR extender, which can be addressed by radio from a Harmony 1100.
Normally the IR Extender needs "visual contact" to PS3 Adapter to the signals then being able to pass on to the PS3 Slim via Bluetooth. The signal would now be the following:
Harmony 1100 - [RF] -> IR Extender - [IR] -> PS3 Adapter - [BT] -> PS3 Slim.
However, if you look closely, it is noticeable that the PS3 Adapter provides an unspecified 2.5mm jack socket at the back. This connector an existing Logitech now can IR extender be connected directly and it will save you by the infrared path "IR Extender - [IR] -> PS3 Adapter"!

The IR adapter has at the back of 4 x 3.5mm jack sockets to which you can plug in up to four additional IR transmitter diode pairs. One of these jacks can be used to connect the PS3 adapter.

Only drawback is the necessary cable (2.5 mono jack to 3.5 mono jack), which is not available in retail stores and would therefore be to solder itself. It is absolutely a mono-cable necessary, a stereo cable works properly not (at least not on PS3 adapter !!). A solution would be the use of a conventional 3.5mm jack STEREO cable in which one end of a "2.5 mm jack / 3.5mm jack MONO-adapter" is connected. However, the PS3 adapter is always compelling a 2.5mm mono (!!!) - expected jack.

The signal path when direct connection is now the following:
Harmony 1100 - [RF] -> IR Extender / PS3 Adapter - [BT] -> PS3 Slim.