| Parameter | Type | Length (octets) |
|---|---|---|
| Message type | F | 1 |
| Circuit group supervision message type | F | 1 |
| Range and status | V | 3-34 |
2.7 Circuit Group Blocking message (CGB): A message sent to the exchange at the other end of an identified group of circuits to cause an engaged condition of this group of circuits for subsequent calls outgoing from that exchange. An exchange receiving a circuit group blocking message must be able to accept incoming calls on the group of blocked circuits unless it has also sent a blocking message. Under certain conditions, a circuit group blocking message is also a proper response to a reset circuit messa ge.2.8 Circuit Group Blocking Acknowledgement message (CGBA): A message sent in response to a circuit group blocking message to indicate that the requested group of circuits has been blocked.
2.11 Circuit Group Unblocking message (CGU): A message sent to the exchange at the other end of an identified group of circuits to cause cancellation in that group of circuits of an engaged condition invoked earlier by a blocking or circuit group blocking message.
2.12 Circuit Group Unblocking Acknowledgement message (CGUA): A message sent in response to a circuit group unblocking message to indicate that the requested group of circuits has been unblocked.