No Ringback Tone when making outbound calls with Grandstream IP PBX UCM63XX
Description No ‘ringback tone’ issue on outbound calls occurs when the PBX or UCM receives 183 Session Progress (with SDP) first and then 180 Ringing later from the SIP Service Provider (ITSP). It would be a 183 Session Progress message to play the ‘Early Media’ on the caller’s phone. Also, missing SDP in 183 Session … Read more