Z³o¿y³em interfejs wg strony
It's favorable to test the circuit before putting it into operation. All you need is a dual output
adjustable power supply (two series connected 9V batteries do the job, either) and a voltmeter.
1) Set DTR and TXD to +9V referred to GND. The voltage across the dive computer contacts
should become around 3V and the voltage at RXD should be around +8V to GND.
2) Change TXD to -9V (keep DTR at +9V). The voltage across the dive computer contacts should
become zero and the voltage at RXD should be around -8V.
Are these tests successful, you can plug the interface to the PC and see if the Dive Manager
software recognizes it by the test routine. Now you can perform your first data transfer.