We are having an issue where we are receiving one way audio over a SIP trunk between a Cisco Call Manager Server and the Shoretel System. We can make calls perfectly from cisco to shoretel and shoretel to cisco and have no audio problems. The problem occurs if the shoretel user put the cisco user on hold, when they pick back up the cisco phones can not hear the shoretel user. But if the cisco user puts the shoretel user on hold and comes back everything works normally. Any suggestions?