The picture of the "WI232EUR Modem" is a bit misleading because on the 8 Pin Molex the red cable (+ Pole) connects to 5 V on the Tiny. But the Modem is driven via 3.3V (one pin to the left).
Furthermore i do not have to disconnect the two Pins RTS and CTS on the ground station as writen in note 1 and 2.
The Radiotronix Modems are still available. But the company has a new name and the part a new description: It is now named TRM-868-EUR and the Company is Linx - so move it from deprecated to active - its working perfect :-)