Indicates the phone call state of this channel. Valid values are: call-state-VOID (0), -> invalid state call-state-IDLE (1), -> the line is in idle state call-state-DIALING (2), -> the line is originating a call call-state-COLLECT-FIRST-DIGIT (3), -> waiting to collect the first digit call-state-COLLECT-DIGITS (4), -> collecting additional digits call-state-CALL-OFFERED (5), -> the station call request has been offered to the PBX control call-state-PROCEEDING (6), -> the call is in progress call-state-RINGING (7), -> the call has seized a destination line call-state-ALERTING (8), -> the destination has been seized call-state-CONNECTED (9), -> the destination has answered the call call-state-DISCONNECTING (10), -> the call is in the process of terminating call-state-FAILED (11), -> the call attempt failed, wait for hangup call-state-UNAVAILABLE (12), -> destination is not available to receive call call-state-OFFHOOK (13), -> the call has been completed but the phone is offhook call-state-INITIALIZE (14), -> initialize the call object (binds with Conn Mgr) call-state-INITIALIZING (15), -> waiting for the response from Conn Mgr (Inservice Ack) call-state-DIAL-REQUEST (16), -> call object sent up OffhookInd and waiting for ACK call-state-HELD (17), -> the call has been put on hold call-state-FEATURE-INVOKED (18), -> indications that a feature has been invoked and waiting response call-state-OFFHOOK-IDLE (19), -> indicates that the phone is set to offhook and is IDLE call-state-OFFHOOK-ACTIVE (20), -> indicates that the phone is set to offhook and is ACTIVE call-state-OUT-OF-SERVICE (21), -> indicates that the phone is out of service call-state-OUTPULSING (22), -> digits are being sent to the external key or voice mail system