DAU-9P Notebook Edition (atrox)

Allmost all DAU-9(P) circuits and descriptions on the web orginates from a Chech-Hacker. This circuit derives power from two pins of the serial port with a 7805/78L05. The 7805 requires, that the input Voltage is at least 2V higher than the output-voltage (makes 7V). Than there are Diodes to get only the positive Voltage so, summing it up means, that the serial port has to deliver at least 7,7 V for the circut to work.

This is not true for most Notebooks, since their signals are 5,5 - 6,5 V in most cases. Some Vendors use Zehner-Diodes to get 5V, but this may draw to much power from the serial port. My solution is, to use a 7802 and omit the 3 diodes. My tests showed, that 7802 really delivers about 2,5V which is perfect for Nokia phones, since the digital high-level is defined between 2.0 and 2.8 V on a 6110. This is slightly below the recommended max3232 voltage, but at least with the original max-IC it is working.