DETAILED DESCRIPTION OF PREFERRED EMBODIMENT FIG.
1 shows a digital data transmission system comprising a digital data transmission network formed by a number of node stations A1-A4 and interconnecting trunk lines 1-5.
Each node station A1-A4 is interconnected with subscriber facilities or terminal facilities through a low-speed parallel standard interface either directly, such as the subscriber device B3 to the node station A2, or through a serial modem link, such as the subscriber devices B1, B2, B4 and B5 through the corresponding modem links 10, 11, 12, and 13 to node stations A1, A2, A3 and A4.
Furthermore, the data transmission network comprises at least one network management computer 6 which monitors and controls the operation of the network and is capable of configuring and supervising said subscriber interfaces.
Since the invention is concerned primarily with the subscriber interface of the data transmission network and the modem link between the subscriber interface and the subscriber device, it is suitable for all network types in which said modem link is to be controlled by the network management system.
The network may be time-division multiplexed (TDM) or packet switched, and it can be formed by fixed connections or contain cross-connection means which allow unlimited establishment of connections between different subscriber devices.
The most typical network structure is, however, a time-division switched network in which the transmission rate of the trunk lines 1 through 5 is 2,048 kbit/s (E1 standard) or 1,544 kbit/s (USA T1 standard).
The trunk lines may also have unequal rates, such as 64 kbit/s and 2,048 kbit/s.
A few network solutions of this type and apparatuses used in them are described in The Dynamics of Private Wire Networks, A.
M.
Henderson, Communication and Broadcasting, Number 29, p.
31-39.
The invention can be applied e.
g.
in networks described in this article.
The subscriber interface is typically a V.
24/V.
28, V.
24/V.
35 or V.
24/V.
11 interface and its rates are typically 300, 1,200, 2,400, 4,800, 9,600 or 19,200 bit/s
|
Caller ID 
