At 15:32 11/06/97 GMT, Gena wrote: >BTW, does anyone have schema of opto-isolated RS232 driver without >external power supply? I need to communicate via RS232 with device >that is on +48V potential (In tel. exchange as you can guess). You could adapt your own schema just a little bit to include two optos, which seems rather easy (if the negative voltage generation you proposed suits your needs). ------------------------------------- Gerhard Fiedler S‹o Paulo - Brazil