2. CS-1 service plan

The scope of CS-1 covers a certain category of services, known as Type A services. These services have the characteristic of being active at only one end of a connection, i.e. they are single-ended and have a single point of control. "Active at a single end" means that the service concerns only one of the two parties involved in a call, and is entirely independent of services that may be active at other ends of the connection. A single point of control implies that the same aspects of a call can only be remotely controlled by a single SCF entity at a given moment in time. Any other service that does not have these characteristics is identified as type B and falls outside the scope of CS-1. However, as some of these services already exist, such as automatic callback on busy or conference communication, they continue to be provided as a switch-based service and are partially supported by...