One of the most problematic Data-cables is KQ-U8A (by the numerous responses of "happy" users)
The scheme at these Data-cables is built in in USB socket
The two types of Data-cables came across to me under this mark : KQ-U8A SXE - the analogue of Data-cables DCA540, Siemens x65-x75 series phones define it as " plugged in DCA540 ".
The scheme of this Data-cable looks so:
Usually this Data-cable works without censures within the limits of its supported functions. And KQ-U8A WT048000317 - the analogue of DCA510 Data-cables, Siemens x65-x75 series phones define it as " plugged in DCA510 ", or " plugged in " (in the last case the Data-cable demands completion about which will be told below).
The scheme of this Data-cable looks so:
the Scheme of this Data-cable is based on an ARK3116 chip. Very often this Data-cable is not identified correctly (" plugged in ") by Siemens x65-x75 series phones and at its connection to phone causes the immediate switching-off of the last. The reason of these problems is that there are no the necessary resistors in the circuit of a Data-cable for its correct identification by the phone and there is an overvoltage(above +3,6V) on the contact 4 (RXD) of the phones socket. Usually,
The scheme of a Data-cable is connected to a socket connected to phone, as on this circuit:
For the correct identification of that Data-cable by the Siemens x65-x75 series phones, it is necessary to solder in two resistors on 10kom between contacts 2 (GND)-5 (CTS) and 2 (GND)-7 (DCD) sockets of the Data-cable connected to phone. For the solution of the problem of the overestimated pressure on contact 4 (RXD) I suggest to include an emitter follower consummated on any low-power n-p-n transistor in the scheme. It does not exert on the work of the scheme and signal passaging, reducing thus a pressure on the contact 4 (RXD) on 0,6V. At the various forums, devoted to cellular phones, advice came across to me - to solder a stabilitron between contacts 2 (GND)-4 (TXD) a socket of a Data-cable, but, by my experience, it can lead to full blocking of working capacity of the scheme of a Data-cable. The offered scheme of completion of the Data-cable, including addition of missing conductors and providing full compatibility with Data-cable DCA510:
In connection with possible difficulties at a finding of necessary contacts of chip ARK3116 (it is very frequent it is filled in by plastic so, that it it is impossible to define marks of its conclusions) I result the scheme of a Data-cable allowing as much as possible to realize all of function of a Data-cable without addition of missing conductors:
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