RS232 Troubleshooting for Q24CLASSIC



I am using Q24CLASSIC for my GSM project, in which the RS232 communication is working properly at null modem connection, but in case of hardware connection, the communication is not happening because the CTS and RTS pin fron Q24 Modem not going for zero for respective RTS and DTR signals from PC.

Also my modem is not detected by AT commands, it seems RTS and CTS signaling is must, but my device working proper at null modem connection, can you give me your suggestions to rectify this problem.



Maybe the AT+IFC =0,0 helps.


sorry i am not getting any debugging information fron AT+IFC=0


What is a null modem cable if it’s not “hardware” ?! :open_mouth:

You need to provide full details of each case!

Show schematics!


i don’t how to upload my schemtics, better you give me your mail id



You could load it to the site given in this post:

This way not only one person would see it and you might find somebody to help you.

Best Regards,


Dear awneil/jan

this is the link, where the schematics is uploaded, … m.pdf.html

expecting your feedback