HT488 not support incoming caller ID only. NOT 3CX not support caller id from HT488. The specifications of HT503 support
caller ID from both IP and PSTN. However, this feature at HT503 not work for me. I have try a few different type caller id (FSK, BELL and ETSI) analog phone lines. But no luck for HT503. All of them can be correctly decode the incoming caller by Grandstream GXW4104.