We have an issue with a site where any outbound calls where the recipient is engaged reports back as busy, according to the logs, and the initiator of the call is cut off with no indication that the recipient is engaged. There is no tone or visual indication on the phone. The phones are Yealink T19 and T42 devices. The 3CX PBX (v15.5.3849.1) uses a SIP trunk to a BeroNet 1600 device (v3.0.19) with a single PRI (10 trunks) connected. The issue has been there for a short while and predates the most recent firmware update two weeks ago. Is it possible to pass some indication onto the caller that the recipient is engaged?