Hello vhymanskyy, mpo881
Thanks for your information, as a result I made some progress.
After pushing the red power button, I got the following A7 responce:
^CINIT: 1, 0, 0
^CINIT: 2, 32, 41891
^STN: 37
^CINIT: 4, 8192, 37
^CINIT: 8, 2048, 1
^CINIT: 16, 0, 1638420
^CINIT: 32, 0, 0
+CREG: 0
on a pc terminal program.
But sending an AT command did not resulted in a OK reply, as a Siemens TC35 does.
With a scoop I checked the A7 URXD pin voltage levels and saw a signal between 0 and 2.5 V,
I hope you have an idea.
Thanks