Checking access authorisation to a signal processing system

COMPLETE SPECIFICATION (ORIGINAL)

FOR OFFICE USE:

Tbu document oontaku da »raen«kne»ti made uatar Section 4V.

t » f t « c « ί

Hit

Class

Complete Specification Lodged:

Accepted:

Published:

Int. Class and ia comet tar pttattag.

ι r .....-.......

<img file="AU593554B2_D0001.tif" />

« ε £ t ε &lt;

C « I ε έ &lt; : u s

<td> Priority: Related Art:</td><td></td><td></td><td> LODGED AT SUB-OFFICE 2 7 MAY 1986</td><td></td>

<td rowspan="2"> Name of Applicant:</td><td rowspan="2"> SIEMENS</td><td></td><td> ~^- Sydney</td><td></td>

<td colspan="2"></td><td></td>

<td> Address of Applicant:</td><td colspan="3"> Wittelsbacherplatz 2, D-8000 Munchen Federal Republic of Germany</td><td> 2,</td>

JOHANN FRANZ WURZENBERGER

Actual Inventor:

Address for Service:

Spruson &amp; Ferguson, Pate»fc Attorneys, Level 33 Sfc Martins Tower, 31 Market Street, Sydney,

New South Wales, 2000, Australia

Complete Specification for the invention entitled:

METHOD AND CIRCUIT APPARATUS FOR CHECKING THE AUTHORIZATION OF ACCESS TO A SIGNAL PROCESSING SYSTEM

The following statement is a full description of this invention, including the best method of performing it known to us

SBR/TGK/164T '^,!faS&lt;r;s

- .‘mf’

ABSTRACT OF THE DISCLOSURE

For checking authorization of access to a signal processing ' system (SVS) from designated peripheral units (TE, BS) connected with the system, for the purpose of transmitting and, if the occasion arises, receiving signals, it is provided that a keyword is entered in the signal processing system for esuh peripheral unit. Such a keyword is always derived from a code number allocated to a respective peripheral unit and from identification data which is freely selectable for the respective peripheral unit. In the event of an intended access by a peripheral unit, the code number transmitted by said peripheral unit and the identification data pertaining thereto are combined with the keyword allocated to the respective peripheral unit.

i t ♦ ci « 4 » t * t fc t &lt; t c c s e c t H ; fc fc fc t fc • i ·

3s*. ·'

<img file="AU593554B2_D0002.tif" />

Φ fc C C

<img file="AU593554B2_D0003.tif" />

BACKGROUND OF THE INVENTION

<img file="AU593554B2_D0004.tif" />

1. Technical Field

The invention relates to the field of signal processing generally and, more particularly, tp a method and circuit apparatus for checking the authorization of access to a signal processing system from designated peripheral units.

2. Description of the Prior Art » »1 i * * t * ι

111t t ft l ft€ •C € « ' e f t f r ’20.

C -: ί

I ft t V ft t € t ft 1 « ftft ft ft ft ft. ft ft ft ft ft * « t t, t C

Peripheral units are connected to a signal processing system for the purpose of transmitting and, if the occasion arises, receiving signals by means of a code number allocated to each peripheral unit tind by means of identification data freely selectable for the respective peripheral units. Signal processing systems which can be ' accessed from peripheral units are frequently provided with units which, in the event of an intended access from a peripheral unit connected to such a signal processing system, first of all check the access authorization of the relevant peripheral unit. -Such a signal processing system can, for example, be found in private and public communications systems as well as in data processing'systems which offer specific services to external subscribers. The examination of access authorization, similar to the subscriber identification in a videotex system known from German OS 28 42 777, can be performed, e.g.,,in such a way that a specific code number, for example, a specific, calling number, is allocated to each of the peripheral units. In the event of an intended access, the specific number is transmitted from a peripheral unit to the signal processing system, together with freely selectable identification data for the particular peripheral unit. An examination of the access authorization by means of said code number and the associated identification data, however, has the disadvantage that forgeries — ' in particular, through repeated manipulation — of code numbers and the associated identification data cannot be precluded.

<img file="AU593554B2_D0005.tif" />

A ftl

\v

<img file="AU593554B2_D0006.tif" />

c c r

C f I t s

: ·- s t fete t St tt ί

Γ \ ?.o t * *

<img file="AU593554B2_D0007.tif" />

SUMMARY OF THE INVENTION

It 1s the object of the present Invention to disclose a method whereby more secure checking of the access authorization from peripheral units is feasible, to a large extent, by means of a novel method and circuit apparatus of the abovementioned type.

In accordance with the present invention there is disclosed a method of authorizing access to a signal processing system from a designated one of a plurality of peripheral units within said system, wherein each said peripheral unit is connected to said system for the purpose of transmitting and/or receiving signals by means of a unique code number allocated to each said peripheral unit by said system and by means of identification data freely selectable by users for each said peripneral unit, wherein said method comprises the steps of:

said system providing a keyword that is not known to users or operating personnel of said system for each peripheral unit in said signal processing system, said keyword being always derived from said specified code number and said identification data for each respective peripheral unit:

furthermore, in the event of intended access from a peripheral unit, initially said code number and said identification data are transmitted for said purpose by said peripheral unit; and said signal processing system uses said code number to select the respective keyword, wherein each of said code number, identification data and keyword are subjected to combinatorial circuitry;

whereby access to said signal processing system is obtained when the output signal of said combinatorial circuit is compared with a preset value and found to correspond to said preset value.

The present invention offers the advantage that, by combining several data, namely the code number, the Identification data and the keyword, the access authorization can be checked with a high degree of security. This degree of security is achieved, in particular, by the fact that two types of data to be combined are not simultaneously accessible to users or the operating personnel of the signal processing system. The signal processing system 1s thus provided only with the keywords allocated fo the individual peripheral units. Furthermore, the procedure for defining said keywords are not known either to the users or to the operating personnel of the

<img file="AU593554B2_D0008.tif" />

© r v

- 3A signal processing system. Finally, the identification data are defined in a freely selectable way by the users of the signal processing system upon placing a peripheral unit into operation, and they are not entered in the associated signal processing system.

The method according to the present invention may also prove advantageous for checking the access authorization from a control &lt; PS &lt; s ·' 5 t c f s s r

Hi f U € t r r t

<img file="AU593554B2_D0009.tif" />

IA0/671O

<img file="AU593554B2_D0010.tif" />

tl «t ί ί f fits station of the signal processing system to data stored in said signal processing system. Prior to obtaining access to such data, the access authorization may be checked by means of a code number allocated to one of the relevant control stations, the freely selectable identification data for the relevant control station, and a keyword entered in the signal processing system for the relevant control station.

Moreover, the method according to the invention also proves advantageous for checking the authorization to activate the control sequences relevant to the operation of a signal processing system from a control station ^!of said signal processing system. Prior to an activation of control seauences, the access authorization concerning the relevant control station may be checked by means of a code number allocated to the relevant control station, the freely selectable identification data for the relevant control station, and a keyword &lt;entered in the signal processing system for the relevant control station.

<img file="AU593554B2_D0011.tif" />

, ,20 The advantage offered by the two abovementioned applications is that only authorized operating personnel have access to the data stored in the signal processing system or are entitled to activate ¹ specific control sequences concerning the operation of the signal

V,/ processing system· t t« . , ' ' «' In addition to the abovementioned code number and identification data, a defined system code number can be integrated into the _t derivation of the keywords and the checking process of access authorization. This offers the advantage of further increasing ζ ’ t 3P security in checking the access authorization to a signal processing system.

A . Λ - ' ; / . - ^: ' In addition, the method according to the present application \ offers the advantage of identifying calling and/or called subscriber

I ti

- 4 terminals of a packet data switching cunter integrated in the connections which run through a packet data switching center of a

- packet switching network. With this method, such an identification is performed in such a way that, when placing into operation the · 5 respective communications channel, a keyword is entered in the packet data switching center for each subscriber terminal communicating with the packet data switching center via a communications channel, which in the packet data switching center is derived from the specified freely selectable identification data and the calling number

1() allocated to the respective subscriber terminal. In the course of establishing a connection, the calling number allocated to the respective subscriber terminal is transmitted in addition to the respective identification data in a data packet initiating said · establishment, and the transmitted calling number and the associated identification data are always combined with the keyword allocated to

9- 4 fe ^: ' , ’«*«»’ the respective subscriber terminal for identification.

♦« &lt; &lt; ' -

I - . ' :

«. ' « € C - ^{: :}

Preferably, an initiated connection is continued only in the event of a correct identification of each of the respective calling t f . - . .

t ^20 and/or called subscriber terminals. This offers the advantage that, in the first place, switching operations in a packet data switching center can be handled only when the respective calling and/or called subscriber terminal can be determined for subsequent collection of ·*Δ&gt; subscriber charges. In the second place, it is possible to block the 25 setting up of connections for specific subscriber terminals, for t 1 &lt; .

Δ) »* example, by cancelling keywords. The setting up of a separate list , of blocked subscriber terminals in the respective packet switching center thus becomes superfluous. For practical purposes, with ’ ' subscriber terminals connected with the packet data switching center ^s, 30 through a private branch exchange (PBX), separate identification data can be selected for said subscriber terminals, by an operator of the PBX. This provides a simple method of call record logging for the individual subscriber terminals of the PBX.

<img file="AU593554B2_D0012.tif" />

ft ft β ft ft · ft &lt; ft • · ft ft ft ft ft ft « ft ft ft I ft » « ft ft ft ft ft

‘.2,0 ft « i ft ft « ft ft « ft » βft © « ft ft « ft ft ft · • « β ft β ft ft ft &gt; ft « ft ft ft

V

<img file="AU593554B2_D0013.tif" />

t i « t ♦ ft : ft ft t t

If various optional services provided by operators of switching networks are used by the individual subscriber terminals, it is practical, with one data packet to initiate the establishment of a connection, and to transmit data signals requesting services which data, after an identification of the respective subscriher term!nal, can be accepted as actual parameters. This offers the advantage that the services provided by switching network operators can, as a matter of fact, be used only by authorized subscribers.

Circuit apparatus for performing the method in accordance with the present invention can be realized with relatively low expenditure in circuitry due to the fact that the signal processing system has a memory configuration with a number of storage cells corresponding to the number of peripheral units, which storage cells are used for storing the keywords allocated respectively to the peripheral units. A first register is provided fO’· buffering a code number transmitted by one of the peripheral units, and a second register is provided for buffering the identification data pertaining to its respective code number. Also, a combinatorial circuit is connected with said registers and the memory configuration, which combines both the code numbers fed by said registers to said combinatorial circuit and the identification data pertaining to said code numbers with the keywords corresponding to the respective coae numbers.

In the following description, the present invention is explained in detail by way of examples and in the drawings,

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a block diagram of a signal processing system in accordance with the invention;

Fig, 2 shows the design of a schematic identification Configuration shown in Fig. T;

ft I ft ft t

i ' ί ^: &amp;

SBR/JS/0400P

R-

<img file="AU593554B2_D0014.tif" />

' Fig. 3 shows a possible design for a combinatorial circuit provided in the identification configuration according to Fig. 2; and

Fig. 4 shows a block diagram of a packet switching network as a further application of the present invention.

DETAILED DESCRIPTION

Fig. 1 shows a section cf a signal processing system SVS. This system can, for example, be a communications system of either a private or public communications network. However, said system can also form a data processing system which external users may access for specific services in the field cf data processing. The signal processing system is interfaced with a number of peripheral units TE. Depending on the type of associated signal processing system, said peripheral units may be developed from conventional data ‘terminals for the purpose of receiving and/or transmitting data signals. Moreover, the siginal processing systems SVS is connected with a control station, designated as BS, which serves as an additional peripheral unit through which the operating personnel can gain access to the signal processing unit for the purpose of maintenance and servicing. ·

Fig. x Shows a central processing unit VE of the signal processing system SVS. Further, the central processing unit VE merely indicates the existence of a central control unit CPU as well as a memory unit connected with said control unit through a bus system, comprising read-only memories ROM and read-write memories PAM. Said central processing unit VE is connected with a transmitterreceiver configuration ,SE through which said peripheral units TE and the cpntrol station gain access to the processing unit. Finally, the central processing unit and the transmitter-receiver configuration are also connected with the input of an indentifier configuration ID. The output of said identifier configuration is interfaced with a control input of the transmitter-receiver configuration.

£ ft «

I ♦i \ j

, With reference to Figs. 2 and 3, the following is a detailed description of the method of checking access authorization to the . signal processing system SVS.

To each of the peripheral units TE and the control station 3S is allocated a separate code number by the signal processing system, and . to a transmission system, a ceiling number. In the start-up of the signal processing system, a keyword is formed for each peripheral unit and the control station after the mathematical operation has been defined, said keyword being formed by means of the respective allocated code number and the identification data, which are freely selectable by the user of the respective peripheral unit or by the control station and represents a code sequence. Said keyword is · stored in a memory SWS (Fig. 2) of the identifier configuration ID ,’¹,⁵*, for the period during which the respective peripheral unit or control « «*· ,,,, station is interfaced with the signal processing unit, or until a ^keyword has been redefined. Said memory is provided with a position ' ^r ‘ input LE for receiving keywords and is so arranged that for each of the peripheral units TE and control station BS a storage cell is reserved for keyword input. The defined mathematical operation, whereby the individual keywords are determined, is .not known either to users or operating personnel of the signal processing system. Furthermore, the identification data defined by users are not ' accessible to the operating personnel. Only authorized personnel at , 25, the operatina console are familiar with the defined identification « » I ,.

H t I , , data.

•»_t If it is intended, for example, to access the signal processing , system SVS from one of the peripheral units, that peripheral unit is f β

3CX requested to transmit the code number allocated to it, as well as its identification data. For the purpose of buffering said data, the identification configuration ID (Fig. 2) is provided with two separate registers, namely a code number register KF and an identification data register IIR, which receive the data fed from the transmitter-receiver configuration SE via a bus system BUS1 and BUS2, respectively.

By means of the code number buffered in the register KP., the abovementioned memory SWS is now selected via a bus system BUS3 for reading out the keyword which is stored in said memory for the peripheral unit designated by said code number. To said readout keyword, which arrives via a bus system BUS5, and the data stored in the registers KR and IIP which are provided, on the one hand, via. bus system BUS3 and, on the other hand, via bus system BUSA, a combinatorial circuit VS (Fig. 2) is subsequently applied. Said combinatorial circuit subjects the input signals, which are fed to it

10. in the form of input variables, to a predefined binary mathematical operation. Then the binary output signal occurring at the output of the combinatorial circuit provides details of the result of the check of the access authorization to the peripheral unit concerned. If, for example, the output signal corresponds to the defined expected ,’,Ί'ό, value, the peripheral unit TE in question is authorized to gain t t a , ^: . ' t,,, access to the signal processing system SVS.

For these checking procedures, depending on the type of requested security, any binary arithmetic linkages can be designated as mathematical operations for determining keywords as well as for the checking of access authorization by means of the combinatorial circuit VS. It is merely required that the two designated arithmetic linkages must be so synchronized that, after the access authorization ' -⁶* has been checked correctly, a preset expected value appears at the

- *«2.5 output of the combinatorial circuit. An example of a possible ‘ embodiment of the combinatorial circuit VS is shown in Fig, 3. The combinatorial circuit VS shown has a number of AND elements Gil ·», through Gin corresponding to the number of information bits

S fl fl fl . . . . : , ; .

· pertaining respectively to the input signals. Said AND elements are id developed with three inputs through which, they are connected with lines of the bus systems BUS3, BUSA and BUSS, which feed the respective information bits. The output signals of the AND elements Gil through Gin are fed to another AND element G2 which has a number of inputs corresponding to the number of said AND elements Gil to

<img file="AU593554B2_D0015.tif" />

Gin. The output of said AND element G2 forms the output of the combinatorial circuit VS.

The above-described intended access to a signal processing system SVS from one of its peripheral units TE is permitted only after correct checking of the access authorization, which is indicated to the transmitter-receiver pairs SE from the combinatorial circuits VS as shown in Fig. 2.

ΪΒ.

♦ κι ί t v

<img file="AU593554B2_D0016.tif" />

IH t

<img file="AU593554B2_D0017.tif" />

In the preceding discussion, the checking of access authorization was explained with examples relating to a peripheral unit TE. The procedural sequences corresponding to the method explained above apply also to access to the signal processing unit intended by a control station BS. Such an access may, for example, be necessary for maintenance dnd servicing. At the same time, the checking procedure of access authorization described above ensures that, only selected personnel can access the data stored in the signal processing system or can activate specific control sequences required for operating the signal processing system, It must also be pointed out that, in order to gain increased security in checking access authority, a separate system code can be allocated additioriallv to each signal, processing system, said codes being included respectively as additional input variables in the abovementioned synchronized mathematical operation pursuant to Fig. 3 for the purpose of forming keywords and checking the access authorization to be performed by means of the shown combinatorial circuit VS, For said purpose, the identification configuration ID can, for example, as Indicated- in Fig. 2, have an additional register Reg connected with the combinatorial circuit VS, in which the system code for the associated signal processing system is stored,

The process described above for checking access authorization ssh also be applied advantageously to Identify called and/or callin'; subscriber terminals in a relevant packet, data switching Pn

<img file="AU593554B2_D0018.tif" />

J

<img file="AU593554B2_D0019.tif" />

I • · · ft ♦ • *« ft terminals are associated with switched connections which run via packet data switching centers of a packet switching network. Fig. 4 shows a schematic Jrawing of such a packet data switching network, designated with the letters PN. Said packet switching network can, for example, be formed by the two packet data switching centers PV1 and PV2 which are interconnected through a transmission line. Such packet switching centers can generally be connected to a numer of subscriber terminals. However, for the purpose of simplification, Fig. 4 shows only a limited number of connected subscriber lines. For example, only one subscriber terminal, designated TS1, is connected with the packet switching center PVl. This may be a packet-oriented subscriber termin',! which enables transmission of data signals in accordance with CCITT recommendation X.25.

Subscriber terminals TS2 through TS5 are connected with the packet data switching center PV2. In particular, the subscriber terminal TS2 is shown directly connected with the packet data switching center, i.e., a subscriber terminal able to receive and transmit data signals in packet form. The subscriber terminals TS3 and TS4 are connected through a PBX NST with the packet switching center PV2, Said PBX can be so developed that data can be exchanged in the form of packets between PBX and the associated packet switching center. And finally, the packet switching center PV2 is indirectly connected with a circuit switching center DV of a circuit switching network. The circuit switching network can, for example, be a telephon network. As such telephon networks dohot transmit connection setup signals or data signals in the form of packets, said signal cannot be, r*,

<img file="AU593554B2_D0020.tif" />

ft Μ I * ft ft » ft ft tr

<img file="AU593554B2_D0021.tif" />

* ί

<img file="AU593554B2_D0022.tif" />

I

SBR/3S/O4OOP

L . - :

<img file="AU593554B2_D0023.tif" />

r transmitted between the circuit switching center DV and the packet switching center PV2. On the contrary, what is required of the signals

J is a signal conversion. Therefore, the packet switching center PV2

XI shows in Fig. 4 a signal converter designated .PAD. When a signal is jj transmitted from the circuit switching center DV to the packet switching i center PV2, said converter, for example, first converts the signals

I transmitted in a start-stop format into packets. And when a signal is transmitted in the opposite direction, a corresponding conversion of said packets into signals with a start-stop format will take place.

Said conversion functions are also known as packet assembly disassembly functions.

Irrespective of the abovementioned types of connections used in individual cases for connecting subscriber terminals to a packet switching center, it is necessary for the purpose of subsequent call ft ftft «ft β • ftft tt « ft ft ft ft ft ft ft ftft ft ft ft ft ft • ft ft ft ft ft ft • ftftft ft ft ft ft ft t ft ftft *.

<img file="AU593554B2_D0024.tif" />

# ft-«' ft ft ft ft ft ft ft ft ft ft ’ ft ft ft ft ft ft ftft ftft ft ft ftft ft ft * ft ftftft ftft ft ft ft ft • ft ft ft ft t

SBR/JS/0400P

<img file="AU593554B2_D0025.tif" />

b ··»':· w,- 12 •S &gt;

/71

I ί tl !

j ’ T record logging, for example, or the utilization of services provided by the operator of the packet data switching center — for instance, • the allocation of a closed user group class of service — clearly to identify the subscriber terminals in the packet switching center which initiate the connection setup. In order to perform such an identification, the two packet switching centers PV1 and PV2 shown in Pig. 4 are provided respectively with the Identification ' configuration ID described above. Said identification configuration is connected at the input side with the transmitter-receiver pair SE1 &gt; and SE2 through which each packet switching center receives or , transmits data signals in the form of packets. At the output side, each identification configuration is connected with the respectively associated transmitter-receiver pair.

’.Γ5-. When placing into operation a communications channel of a packet switching center — for example, packet switching center PV2 shown in tit .

urt' Pig·. 4 — for the purpose of connecting a packet-oriented subscriber *' ^c terminal or a subscriber terminal through a converter, a keyword is' ' formed in the manner described above by means of the calling number

20' defined for the relevant subscriber terminal.· andby means of the identification data which is freely selectable by the user of the , , subscriber terminal. For the period during which the communications channel which has just been placed in operation is in service, or * « * “ until a keyword has been redefined, such a keyword is then stored in

2*5·, a memory of the identification configuration ID pertaining to the ft« t . : ' relevant packet switching center, said memory being in conformity with the memory SWS shown in Fig. 2.

ft &lt;

* e € _:^stf f ' If, for example, a connection is to be set up from a packet-oriented subscriber terminal — for example, the subscriber terminal TS2 ih Fig. 4 — with another subscriber terminal -- which may be the subscriber terminal TS1 shown in Fig. 4. — a, packet (for an incoming call) must first be transmitted from the calling subscriber terminal TS2 so as to initiate the connection setup. Said . V ' ' · ' -13- . .

<img file="AU593554B2_D0026.tif" />

!

r

I ί

ί'

I ί ft ft ft ί · ♦ ft

I ., * »« i » t U ft ‘ » M t i t v ft c · ; » C &lt;

%2-fi t k · • ft ·:

t t r ft « t ft » 4 ft ft ft ft ft » ft « &lt; t

I

<img file="AU593554B2_D0027.tif" />

ft ft I ft ft ft ft ftft ft ί (( * t I ft t &lt; i ft ft ί · ί t · packet contains, among other things, the calling number of the subscriber terminal TS2 and the selected identification data. By means of the identification configuration ID shown in Fig. 2 and 4, said calling number and the identification data are then employed for the identification of the subscriber terminal TS2 in the same manner described above for the checking procedure for access authorization to a signal processing system.

Only in the event of a correct identification by the combinatorial circuit shown in Fig. 2, which in this case is indicated to the transmitter-receiver pair SE1, will the connection setup initiated by the subscriber terminal TS2 be continued. This, for example, will ensure that a connection will only be made if the calling subscriber terminal is identifiable for call record logging.

On the other hand, the fact that a connection is fully set up only in the event of a correct identification of the calling subscriber terminal is also used for targeted blocking of outgoing calls from subscriber terminals. Then it is possible by the targeted cancelling of keywords to result in a lockout for the subscriber terminals allocated to said keywords. Separate 1ists of subscriber terminals blocked for outgoing calls are, therefore, not necessary.

In the process of continuing the connection setup, packets must be exchanged in compliance with CCITT recommendation X.25 between the relevant subscriber terminals, in this case the subscriber terminal TS2 and the packet switching center. However, this known exchange will not be described in detail.

In the preceding, the identification of a calling subscriber terminal was explained only in the example of the packet-oriented subscriber terminal TS2, The operational sequences corresponding to the above described sequences are also performed when the subscriber terminals to be identified are connected, fof example, through a

<img file="AU593554B2_D0028.tif" />

fi \\

--14SBR/JS/0400P ϊΛ

<img file="AU593554B2_D0029.tif" />

ft · · • 'Λί*

Ul-t *

urt f C ί f ί .2‘5.

ί ft« * ft « * ft ft· fi ft ft • f t &lt; V- ft • ( ς&gt;

converter (PAD in Fig. 4) of the packet data switching center. In such a ease, a so-called two-stage selection will occur. In the first stage, an access number for the packet switching network is transmitted, and, in the subsequent second stage, a selection procedure for the packet switching network will occur. For example, in said procedure, the calling number, the selected identification data, and the calling number of the called subscriber terminal are transmitted as selection data in the form of start-stop signals from a subscriber terminal, using an asynchronous transmission method, and are then entered in a corresponding packet by the converter PAD.

Finally, it was also indicated above that subscriber terminals can be connected via a PBX (NST in Fig. 4) with a packet switching center. In this case also the calling subscriber terminal is identified in the'manner described above. Each of the subscriber terminals connected with the PBX's can be provided with separate identification data, so that, for example, call record logging can be performed for the individual subscriber terminals. ’

In addition, apart from the calling number of the calling subscriber terminal and the identification data, information signals requesting specific services can also be transmitted with a packet for the purpose of initiating a connection setup. In such a case, it is advantageous for said information signals to be accepted as actual parameters by the packet data switching center only when the calling subscriber terminal transmitting the packet has been correctly identified. This ensures, for example,.that only authorized users are entitled to use specific' -services.

♦ ^:

The above describes only the process for identifying subscriber stations, using a calling subscriber 'kerminal as an example.

However, in certain cases it may also be necessary to obtain the identification of called subscriber terminals, for example, when charges are assumed by the called subscriber or when called b · -15Sr,

<img file="AU593554B2_D0030.tif" />

fc . . t

Λ

<img file="AU593554B2_D0031.tif" />

ι * 5 ft ,

0 « β

β«β« » « ♦ ί Λ · · ft * ft ft ft ft t ft ft ft ft ft £ t ί ' ζό subscribers are allocated to closed user group classes of service.

The process described above is also advantageous for this type of identification. The information required for such an identification, namely the calling number and the identification data, will in this case be transmitted from the iaspective called subscriber terminal, together with the call confirmation as a reply to an outgoing call, to the applicable packet data switching center.

As for the rest, the packet switching centers PV1 and PV2 shown in Fig. A can also be connected with control stations corresponding to the control station BS shown in Fig. 1, through which selected personnel are able to access the data stored in the respective packet data switching center.or to activate the control sequences required for operating the respective packet data switching center. · . . Thus., there has been described a method and apparatus for checking authorization to access a signal processing system which · should only be considered to be limited by the scope of the claims which follow.

<img file="AU593554B2_D0032.tif" />

<img file="AU593554B2_D0033.tif" />

ft ft ft ft ft . ftft- ft £ ι 4

f. &lt;· ί ί

<img file="AU593554B2_D0034.tif" />

<img file="AU593554B2_D0035.tif" />

w

_t