It is easy to reduce the number of levels by wider networking. However, this is sometimes not possible for topological and/or economic reasons.

If necessary, the number of levels can be reduced by synchronizing the transmission equipment (the transmission network) from the system on level = 1 or = 0. In this way, all systems directly synchronized by the transmission equipment are assigned to level = 2 or = 1. Due to the fact that a connection can go from one system to a third bypassing the second, the actual route can become longer. This is only possible since the route length of the transmission can, theoretically, be up to 27,000 km according to the standards. However, this shifts responsibility for network synchronism to the transmission system. It should also be noted that in the case of intelligent transmission networks - where automatic changeover includes synchronization - the transmission network must be included into the network synchronization plan and into network management. Therefore, the network must be treated as a separate hierarchical level as known from the OpenScape 4000 system. This treatment reduces the number of possible OpenScape 4000 levels; for the transmission equipment networking clock generators may become necessary.

( --> SDH, Special cases)

Annotation 1: Networking clock generator in level 1 or 1 and 2 necessary

Annotation 2: Connecting lines _______ represent clock-transparent digital connections between the systems. Analog and VoIP connections must not be displayed as connecting lines in the clocking plan.

Annotation 3: The numbers at the connections between the systems are a suggestion for priority assignment in the reference clock table (REFTA)