haroonrashid
New Member
Hi Every one... I need any expert's help please... I am handling one device (circuit) which works as to switch on 240 VAC Electric device....and its using RS232 protocol and using only 3 pins of Serial Com Port (2 signals only) (1. Ring Indicator (RI) 2. Data Carrier Detect (DCD)) as input from External Serial Modem...... now my concern is....I want to use External USB Modem....but can't classify how??? Can anybody please help me....???? its quite urgent....Thanks in advance.