[Failed] attempt to make T-DisplayTel work over OCTOI

Setup:

T-DisplayTel --S0--> PBX --S2M--> yate --S2M--> Portmaste3 --TCP--> socat/neu_ulm

Files:

btx-tdisplaytel-tcp.pcap    PCAP file containing TCP stream between PM3 and socat/neu_ulm
neu_ulm_output.txt          console output of socat/neu-ulm
radius-pm3-callcheck.txt    radius config snippet for PM3 forwarding the ISDN call over TCP
displaytel-139-rx.raw       raw bitstream of ISDN B-channel in DisplayTel uplink
displaytel-139-tx.raw       raw bitstream of ISDN B-channel in DisplayTel downlink
displaytel-pm3-btx.mp4      video recording of T-DisplayTel screen when trying to dial up


Things tried (unsuccessfully):
* Non-empty Benutzerkennung/Mitbneutzer/Password/...