We have Yeastar TA 2400 FXS gateway and Alcatel PABX system.
When a connection is established (a call from an analog subsriber to an IP PBX subsriber), when trying to put a call on hold (MusicOnHold) the Yeastar TA 2400 equipment received an INVITE message (Alcatel PABX is initiator of call) with the media attribute a=sendonly parametr in the SDP session and activate MusicOnHold on it's side, which is incorrect.
Yeastar TA 2400 uses the Asterisk telephony package as it's base. Asterisk version 184.108.40.206. This problem is present in the version of Asterisk 1.6