Chetan, On 6/13/07, Chetan Bhargava wrote: > 74LS05 is open collector while 74LS06 is not. Also, Is your Vpp okay? 74LS06 seems to be OpenCollector too. It says "Hex Inverter Buffers/Drivers with Open-Collector High-Voltage Outputs" for SN74LS06 in the datasheet I have. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist