Telephonic communications – Concentrator or trunk selector – Concentrator-distributor pair
Reexamination Certificate
1999-11-19
2004-02-24
Foster, Roland G. (Department: 2645)
Telephonic communications
Concentrator or trunk selector
Concentrator-distributor pair
C379S142130, C379S251000, C379S373030
Reexamination Certificate
active
06697482
ABSTRACT:
The present invention relates to a method and a system for transmitting messages to subscribers during the set-up stage of incoming calls and, particularly, to subscribers to an access system connected to a local switching exchange by means of two-wire telephone interfaces.
BACKGROUND OF THE INVENTION
The transmission of messages prior to the off-hook of the telephone handset in an incoming call, known as “ON-HOOK DATA TRANSMISSION”, i.e. transmission of data while the telephone handset is on-hook and before starting the sending of the ringing current, is specified in the ETSI (European Telecommunications Standards Institute) standard ETS 300 659-1. Said standard defines the procedure to be followed by both the local switching exchange and the subscriber telephone terminal in order that the messages transmitted (calling subscriber identity, date, time, etc.) be displayed to the called subscriber while the telephone is ringing.
Said procedure defines several stages, starting with the sending from the local exchange of a warning indication to the telephone terminal, followed by the transmission of the message to be sent, previously modulated into the audio band, and followed finally by the ringing tone which causes the telephone terminal ringer to start ringing.
The stages mentioned above have a predetermined duration, and the interval of time that elapses between each of the stages is also specified. When the connection of the telephone terminal is made directly to the local switching exchange over the two-wire telephone line, and whenever the local switching exchange and the subscriber telephone terminal can support the message display service in accordance with the aforementioned ETSI standard, there is no problem in running the procedure. Exceptionally, errors can arise in the message as a consequence of noise being induced in the telephone line, but in any event this effect shall occur on very few occasions, sufficiently low to be considered as negligible.
Nevertheless, when the connection between the local switching exchange and the subscriber telephone terminal is set up through an access system the resources of which are shared by all the subscribers to said access network, it can occur that even though the local switching exchange and the subscriber telephone terminal comply with the ETSI standard ETS 300 659-1, it is not possible to guarantee the correct operation of the message display service due to the delays that could arise in the call set-up stage.
In addition, when the connection between the access system and the switching exchange is made over 2 Mbit/s links, with or without concentration (for example, V5.1 or V5.2), the switching exchange employs a procedure in which one stage of the procedure is not initiated before acknowledgement has been received from the access system with respect to the preceding stage.
An access system typically consists of a central access node, which makes the connection with the local switching exchange, and a set of network terminations, to which the telephone terminals of the end user are connected.
The central access node serves to allocate the access system resources (traffic channels) which are shared among all system users. Said allocation of resources is achieved by means of signalling messages generated as a result of detecting incoming calls (to system subscribers) or outgoing calls (from system subscribers). A dialogue is therefore set up between the access system elements (central access node and network terminations) in which agreement is reached on the resources which are to be employed from among those presently available to all the subscribers connected to the access system (shared resources) and which will serve as support for the call being set up.
To perform all the system management functions, the central access node is formed by a set of units with the following associated functionalities.
interface with the local switching exchange;
system resources management;
interface with the network terminations;
supervision of system elements.
For their part the network terminations serve to handle the calls from or to the telephone terminals that are connected to them, replicating the operation of the local switching exchange. For this reason, the network terminations are formed by a set of units with the following functionalities.
interface with the telephone terminal;
interface with the central access node;
telephone signal processing;
alarm transmission to central access node.
When the local switching exchange supports the on-hook data transmission service, the telephone terminal connected to the access system network termination has to permit the displaying of said messages sent during the call announcement stage.
The sequence of events transmitted by the local switching exchange to the telephone terminal with the telephone handset on-hook, is to be found illustrated in FIG.
1
and is defined in the ETSI standard ETS 300 659-1.
As can be seen from
FIG. 1
, the alert signal (
1
) is first transmitted by the local switching exchange for the purpose of notify the telephone terminal of the imminent transmission of a modulated message (
2
). Said alert signal (
1
) causes the telephone terminal to connect the circuits required for extracting the information sent by the local switching exchange.
In order to permit the telephone terminal to detect the presence of the alert signal and connect its circuits for receiving modulated messages, there is a guard time (T
1
) between the end of the alert signal and the start of the modulated message (
2
). On conclusion of this guard time the local switching exchange will send the modulated message (
2
) in the audio frequency band.
In the same manner as the switching exchange includes a guard time between the alert signal (
1
) and the modulated message (
2
), it also has a guard time (T
2
) between the end of the modulated message (
2
) and the first pulse of ringing tone (
3
) in order for the telephone terminal to detect the end of the message and proceed to disconnect the modulated message detection circuitry. Moreover, due to the characteristics of the ringing tone pulses, and particularly their relatively high voltage, it is necessary to ensure that the demodulator is disconnected when the first ringing tone arrives, otherwise said circuit could suffer damage. From the first ringing tone pulse, successive ringing tone pulses (
3
′) are applied until the destination user off-hooks his handset.
When there is an access system with shared resources situated between the local switching exchange and the telephone terminal, said guard times and events sequence may be systematically altered either through delays in setting up traffic channels for transporting the modulated message, with the possibility of truncating or even impeding message transmission over the access system, or through lack of synchronisation between the local switching exchange events and events replicated into the telephone terminal, leading to disrespect of guard times and consequently endangering the telephone terminal circuitry.
It is therefore necessary to respect the sequence of events and the time intervals between these whenever an access-system is being used between the local switching exchange and the telephone terminal, so as to achieve correct reception of messages sent by the local switching exchange, and avoid damage to the telephone terminal detection circuits.
DESCRIPTION OF THE INVENTION
To overcome the problems mentioned above, the method and system for transmitting messages to subscribers during the set-up stage of incoming telephone calls, object of the present invention, are proposed.
The present invention describes in particular the method and system to be employed in an access system with shared resources in order to provision the on-hook data transmission service when the connection with the switching exchange is established through said access system via a two-wire telephone line.
According to the method of the invention, an access system situated between a local exchange and at leas
De Las Heras Diez Juan Carlos
Martinez Acedo Jose Luis
Alcatel
Foster Roland G.
LandOfFree
Method and system for transmitting messages to subscribers... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for transmitting messages to subscribers..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for transmitting messages to subscribers... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3287872