I am trying to design an rs232 circuit from 2 transisitors. The circuit shown has worked well, except one day when changing the MPU, the MPU receiver transisitor popped. http://flowperformance.com/images/rs232circuit.gif Are there any major flaws with this circuit, and how can I prevent the MPU receiving transistor from popping? Thanks John -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist