M55 custom cable is not detected
 

I have a usb to TTL Serial port which I can use to make an unlock cable for my Siemens M55, I've already connected the Tx, Rx and Ground from the usb cable to the phone but the phone doesn't detect it has a cable plugged and the desktop software doesn't detect the phone either. How can I make the phone detect it?

...normarly,on the Siemens phones is used DCA510 cable (usb to serial). Supplimentarly, you need to connect two resistors, one between pin 5 and 2; seccond between pin 7 and 2 (in the Lumberg connector). For edification, see in attachemment schematic for DCA510 cable (with PL2303 chipset). Search which chipset you have or give the code writed on the cable....
dagos

Thank you very much, now I understand. I will try this when I can get my hands on 2 10k resistors.