Hello Wotan,
there is an IR-LED behind the IR-transparent plastic cover:
IR-TX on the top side of the board, shown here upside down
The black thing right above the TX is the RX.
If the IR-LED is a SFH4045N, as it seems, it has a very narrow viewing angle of +/-9°.
It seems to be driven with a voltage of 1.8V only, with a resistor and a switching transistor in series.
There is no chance for a strong IR-signal In this configuration, unfortunately.
But the cover does not weaken the signal very much.
Cheers, tiki