2.44 User Part Available message (UPA): A message sent in either direction as a response to a user part test message, to indicate that the user part is available. 2.45 User Part Test message (UPT): A message sent in either direction to test the status of a user part marked as unavailable for a signalling point. Table 44/Q.763 Message Type: User part test User part available Parameter Reference (subclause) Type Length (octets) Message type 2.1 F 1 Parameter compatibility information 3.41 O 4-? End of optional parameters 3.20 O 1