The OpenScape 4000 central system has a highly precise clock generator which can be synchronized from various sources. Possible sources include, for instance, digital trunk circuits. The corresponding connection modules can then supply the clock timing in the LTUs 1-15 and synchronize the central clock generator. The AMO REFTA is responsible for configuring which circuits can be used as reference clock suppliers and querying which supplier is currently active.

Access Points of the type AP 3300 IP, AP 3500 IP or AP 3700 IP are connected in asynchronous fashion via the IP network. Thus, the central clock generator cannot be synchronized from LTUs 17-99.

On account of this asynchronous connection, the access point itself is also unable to be synchronized from the central clock generator. Therefore, the HG 3575 module of the access point is equipped with its own highly precise clock generator.

The asynchronism of the clock generators in the OpenScape 4000 central system and in the various access points has no interfering effect on the communication between these components. The jitter buffers required for voice transmission also compensate smoothly for the slight slip between the clock generators.

However, if digital trunk or tie trunk circuits are operated in an access point, the local clock generator must be synchronized with the network clock (“CO Clock“).

To this end, management of the reference clock has been extended with the AMO REFTA. The basic principle is simple:

Thus, in a OpenScape 4000 switch with 83 access points of the type AP 3300 IP or AP 3500 IP, the synchronization of 84 clock generators has to be managed. This means that 84 active clock suppliers (central unit + 83 access points) may exist in such a system.