CA2227189A1 - Access restriction device for a telephone set - Google Patents
Access restriction device for a telephone set Download PDFInfo
- Publication number
- CA2227189A1 CA2227189A1 CA 2227189 CA2227189A CA2227189A1 CA 2227189 A1 CA2227189 A1 CA 2227189A1 CA 2227189 CA2227189 CA 2227189 CA 2227189 A CA2227189 A CA 2227189A CA 2227189 A1 CA2227189 A1 CA 2227189A1
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- Prior art keywords
- sequence
- socket
- dialing
- sequences
- forbidden
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/66—Substation equipment, e.g. for use by subscribers with means for preventing unauthorised or fraudulent calling
- H04M1/677—Preventing the dialling or sending of predetermined telephone numbers or selected types of telephone numbers, e.g. long distance numbers
Abstract
The present invention relates to a telephone socket including two terminals for connection to two respective wires of a telephone line. It includes an access restriction device for preventing a telephone communication upon dialing of a number beginning with a forbidden sequence of digits, the restriction device being connected to the two terminals and including a switch connected between a first one of the two terminals and an additional terminal, the two wires of the telephone line being respectively connected to the second one of the two terminals and to the additional terminal.
Description
ACOE SS RESTRICTION DEVI OE FOR A TEL~ ~ SET
RA~K~ROUND OF l~E lNv~NllON
Field of the Invention The present invention relates to an access restriction device meant to prevent a telephone communication when a forbid-den number is dialed on a subscriber tel~ph~nP.
Discussion of the Related Art Fig. 1 schematically shows a conventional restriction5 device 8, of the type described in PCT patent application WO
95/12266. Device 8 includes a switch K connected to interrupt a telephonP line LT which is connected to a subscriber telephone 10. Switch K is controlled by a microcontroller 12 which receives signals from circuitry 14 for detecting, in particular, an off-hook condition and decoding the DTMF signals carried on line LT.Circuitry 14 is shown connected to line LT between switch K and telephone 10, but it could also be connected upstream of switch K, since it is not meant to operate when switch K is open.
Microcontroller 12 is associated with a ROM including the program to be executed by the microcontroller, and with a RAM
for storing the variables. The RAM stores in particular forbidden and authorized sequences of digits, pro~ r dll~l~ble by the user.
Microcontroller 12 and circuitry 14 are powered by a source 16 which takes the power available on telephone line LT
upstream of switch K.
Fig. 2 illustrates a main application of the access restriction device described in the above-mentioned PCT patent application. A simple telephone installation, especially at a private home, may include several telephone sets 10 connected to respective sockets 20. Teleph~nP sets 10, and thus sockets 20, are connected in parallel to the two wires of teleph~ne line LT.
Access restriction device 8 is connected, as shown, to the two wires which connect the first socket 20 of the instal-lation to an exchange 22. Thereby, device 8 can detect a forbidden sequence dialed from any of telephone sets 10 and interrupt the line supplying all the teleph~n~ sets.
A drawback of this installation is that the wires to which restriction device 8 is to be connected are not always reachable or easy to find, which usually requires the intervention of a professional. As a result, the cost of the installation is most often too high for a private person to be tempted to adopt it.
Of course, an access restriction device may be installed in other places, for example, between a telephone set and its socket. But then, the access restriction is avoided by just plugging another telephone set in the socket.
Summary of the invention An object of the present invention is to provide a telephon~ access restriction device which may easily be installed by a private person and which nevertheless protects an entire telephone installation.
This object is achieved by a tel~phon~ socket including two terminals for connection to two respective wires of a tele-phone line, including an access restriction device for preventing a tel~ph~ne communication upon dialing of a number beginning with a forbidden sequence of digits, the restriction device being connected to the two terminals and including a switch connected between a first one of the two terminals and an additional terminal, the two wires of the tel~phone line being respectively connected to the second one of the two terminals and to the additional terminal.
According to an embodiment of the invention, the access restriction device includes a memory freely programmable by a user to store forbidden sequences of digits; and analysis means connected to the line for acquiring the digits dialed on a telephone set, comparing them to the forbidden sequences stored in the memory and, in case of a coincidence, controlling the opening of the switch to simulate an on-hook.
According to an embodiment of the invention, the access restriction device becomes temporarily inoperative after the dialing on the tel~phonP set of a confidential code, this confidential code being differentiated from a telephone number by the dialing with the code of a first combination of special symbols.
According to an embodiment of the invention, the dialing of the confidential code causes an opening followed by a closing of the switch, the device becoming operative again upon a subsequent on-hook.
According to an embodiment of the invention, a sequence is proyLd~ ble in the memory via the telephone dial after dialing the confidential code with a second combination of special symbols.
According to an embodiment of the invention, the location of a sequence in the memory is identified by the dialing of a location number and of a specific combination of special symbols.
According to an embo~im~nt of the invention, the memory further stores authorized sequences of digits, the coincidence of a sequence with a forbidden number or an authorized number being indicated by an additional information associated with each sequence, the analysis means being adapted to find, among the stored sequences, the longest sequence coinciding with the dialed number, and to control or not the opening of the switch depending on the additional information of the found sequence.
According to an embodiment of the invention, the additional information associated with a sequence is an authorization bit stored with the sequence, this bit being set, upon a programming, by the dialing or not of a special symbol after the dialing of the sequence.
According to an embodiment of the invention, the memory includes a first area for storing forbidden sequences and a second area for storing authorized sequences, the additional information associated with a sequence being provided by the area in which the sequence is stored.
According to an embodiment of the invention, the second area is provided to further store forbidden sequences, the additional information associated with a sequence stored in the second area being supplied by an authorization bit stored with the sequence.
According to an embodiment of the invention, the sequence lengths are stored with the sequences.
According to an embodiment of the invention, the socket includes a cover attached by screws with non-standard drive recesses.
According to an embodiment of the invention, the restriction device includes a dialing circuit for dialing a specific number and then transmitting the contents of the memory through DTMF.
According to an embodiment of the invention, the restriction device includes a dialing circuit, the microprocessor being programmed to cause the dialing of a stored number when no number is dialed during a predetermined time interval after an off-hook.
The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.
Brief Description of the Drawinqs Fig. 1, previously described, schematically shows a conventional access restriction device;
Fig. 2, previously described, shows a conventional arrangement of an access restriction device in a simple tel~phon~
installation;
Fig. 3 shows an arrangement of a telephon~ socket according to the present invention, provided with an access restriction device, in a conventional telephone installation of the type of Fig. 2;
Fig. 4 shows an open perspective view of an embodiment of a telephone socket according to the present invention, provided with an access restriction device;
Fig. 5 shows a general flowchart of the operation of an access restriction device; and Fig. 6 shows an example of a flowchart for managing a list of forbidden and authorized numbers according to the present invention.
Detailed Description The present invention is based on the analysis of the specific way in which the sockets of a simple installation are connected to one another.
As shown in Fig. 2, a conventional telephone socket 20 includes two terminals 20-1 and 20-2 connected to contacts of the socket for cooperating with a plug of the corresponding teleph~n~
set 10. Further, terminals 20-1 and 20-2 of a socket are connected by two wires to terminals 20-1 and 20-2 of the preced-ing socket. The two wires of telephone line LT are connected to the two terminals 20-1 and 20-2 of the first socket 20.
According to the present invention, it is provided to place an access restriction device 8 in a conventional tel~phon~
socket, eventually modified to accommodate the restriction device.
Fig. 3 shows a socket 20' according to the present invention mounted in a conventional telephon~ installation.
Preferably, socket 20~ according to the present invention is the first one. This socket 20' includes, like a conventional socket, two terminals 20-1 and 20-2 for connection to a corresponding telephon~ set 10. Terminals 20-1 and 20-2 of socket 20' are connected conventionally by two wires to termin~ls 20-1 and 20-2 of the next socket 20. However, only terminal 20-1 of socket 20' is connected to a wire of telephone line LT. The rPm~ining wire of telephone line LT is connected to a terminal 20-3 which is a part of restriction device 8. Restriction device 8 is connected to terminals 20-1, 20-2, and 20-3 to constitute the arrangement of Fig. 1, switch K being connected between terminals 20-2 and 20-3. Access restriction device 8 then performs exactly the same function as that of Fig. 2, that is, it disconnects all telephone sets 10 from exchange 22 as soon as a forbidden sequence is dialed on any of the telephone sets.
An access restriction device included, according to the present invention, in a telephone socket 20' is particularly easy to install. Indeed, the first conventional socket 20 is just replaced by a socket 20' according to the present invention and the wires are reconnected to this socket like they were connected in the conventional socket, except for one of the wires coming from exchange 22, which is connected to terminal 20-3 of restriction device 8.
A user with little experience may make a mistake by swapping the wires which are connected to terminals 20-2 and 20-3. In this case, when a forbidden sequence is dialed, device 8 disconnects all telephone sets 10 except the one connected to the first socket 20'. This malfunction may easily be detected by the user, who will thereby swap the wires connected to terminals 20-2 and 20-3 to obtain the correct operation. This connection may, conversely, be voluntary if the telephone set connected to socket 20' is located in a room inaccessible to unauthorized users.
Of course, a socket 20' according to the present inven-tion may be used in an installation with a single telephone set.Terminal 20-2 is then not used.
Fig. 4 shows an open perspective view of an embodiment of socket 20l according to the present invention. As an example, this socket is a T-type socket used in France. Restriction device 8 is in the form of a printed circuit housed against one of the surfaces of a cover 40 of the socket.
Cover 40 is normally fixed to a base 42 by means of two screws. A person who would discover the function of the socket according to the present invention could easily dismount cap 40 and reestablish the unrestricted operation of the socket. To limit such a risk, the screws for fixing cover 40 to base 42 are preferably provided with non-st~n~rd drive recesses, for example triangular, so that only the owner of the corresponding screw-driver can dismount the cover.
To summarize, the operation of a restriction device 8 of the type of Fig. 1 and according to the present invention is the following. Microcontroller 12 is programmed to regularly check the output of off-hook detector 14. When an off-hook condition is detected, the microcontroller acquires any digit or symbol dialed on telPphon~ set 10 via DTMF decoder 14. If the digit acquired in this mAnn~r by the microcontroller corresponds to a forbidden sequence stored in the RAM, the microcontroller controls the opening of switch K during a time which is sufficiently long to be perceived as an on-hook by the exchange.
Two possibilities for controlling switch K may be devised. A first possibility is to imm~;ately open switch K upon detection of a forbidden number. A second possibility is to open switch K only after a predetermined time interval, which enables, instead of forbidding the communication, to limit the duration of this communication. Thus, a pro~ r dllll~ble maximum duration of communication could also be stored in the RAM, for each forbidden sequence. Of course, the counting down of such a duration pref-erably starts when the called telephone set hooks off. Conven-tional circuits to be included in circuitry 14 could detect such events.
The sequences are stored in the RAM during a program-ming phase described hereafter and entered by dialing a confidential code on the telephone dial.
Fig. 5 shows a more detailed general flowchart of the operations performed by the program of microcontroller 12.
At 100, the output of off-hook detector 14 is polled.
At 104, the sequence of symbols or digits dialed on telephone set 10 and provided to the microcontroller by DTMF decoder 14 is acquired. Here, two solutions are possible before proceeding with the next step 106. A first solution is to proceed with step 106 upon each acquisition of a new digit or symbol. A second solution consists in acquiring all the dialed symbols or digits before proceeding with step 106. The end of the dialing of a sequence is detected, for example, by the fact that the user pauses for a time longer than a predetermined delay, or else by the fact that a tone is detected on line LT indicating the ringing of the called telephone set.
At 106, it is checked whether the sequence corresponds to a confidential code stored in the RAM. To differentiate a confidential code from a normal number, the code is dialed, for example, by preceding and following it with special symbols, such as symbols * and #.
At 108, the dialed sequence does not contain a confi-dential code, or the confidential code is wrong. It is then checked whether the dialed sequence corresponds to a forbidden sequence stored in the RAM.
If the dialed sequence is not forbidden, or if it corresponds to a wrong confidential code, an on-hook is awaited at 110, that is, the tel~phone communication carries on conventionally with the numbers which were dialed, until the user hooks on. Of course, in the case where a wrong confidential code was dialed, no telephone communication is obtained, since a confidential code does not correspond to a telephone number.
Conversely, if the dialed sequence corresponds to a forbidden sequence at 108, microcontroller 12 controls the opening of switch K at 112 during a time sufficiently long to be interpreted as an on-hook by the exchange. Switch K is then closed again at 114.
After awaiting the on-hook condition at 110 or the closing of switch K at 114, the microcontroller starts waiting for a new off-hook condition at 100.
If the dialed sequence corresponds to a correct code at 106, it is checked at 116 whether the sequence starts with a specific special symbol, for example symbol #. If such is not the case, for example if the sequence begins with symbol *, an on-hook is caused at 118 by the opening of switch K. m e arrival at step 118 means that the user dialed a correct confidential code with a specific combination of special symbols indicating that all restrictions must be temporarily raised.
Switch K is closed again at 120. This causes a new off-hook, since the user is normally still holding the handset. The user then only has to dial the desired number, which will not be checked by steps 104 to 108. Any number is therefore authorized, even a normally forbidden number, and the communication is carried on normally until an on-hook condition is detected at 110 .
A confidential code is preferably inserted between two special symbols, the beginning symbol indicating a confidential code, and the end symbol indicating the end of the confidential code. As a result, the code can have any number of digits.
Preferably, two-digit confidential codes which may correspond to France Telecom services will be avoided.
Of course, the forbidden sequences as well as the confidential code and other information should be programmable.
The user expresses the desire of programming by preceding his confidential code with a specific special symbol, for example symbol # in the present example (symbol * being used to raise restrictions). Then, step 116 is followed by a programming mode at 122.
In the programming mode, various techniques may be used to input the forbidden sequences in the RAM as well as a variety of associated information. For example, a memory location is identified by a two-digit number framed by special symbols, followed by the forbidden sequence, then by a special symbol to indicate the end of the sequence. The confidential code, so that it can be modified, is stored at a specific location accessible in the same way as the locations containing forbidden sequences.
Of course, the confidential code is factory set to a specific value and provided to the user in the user m~nl]~1.
Once the user has performed his programming, he hangs up the handset, which ends the programming mode at 110.
In the flowchart of Fig. 5, the sequences stored in the RAM have been considered as forbidden sequences. A specific stored sequence forbids the calling of any number which starts with this sequence. Thus, by storing longer or shorter sequences, families of forbidden numbers are defined. For example, in many countries, by storing sequence 00, the calling of any number abroad is forbidden. The storing of sequence 36 forbids, in France, the use of Minitel services. Of course, a sequence may correspond to a complete number.
A disadvantage of only storing forbidden sequences with a small number of digits is that large families of forbidden numbers are defined, which may contain numbers which one may want to use.
To avoid this disadvantage, the present invention provides to also store authorized sequences to define sub-families of authorized numbers within families of forbidden numbers. Then, for example, by storing sequence 36 as forbidden and sequence 3611 as authorized, the calling of any number start-ing with 36 is forbidden, except for 3611 (and any other number beginning with 3611).
Authorized sequences are differentiated from forbidden sequences by additional information. For example, each sequence may be stored with an additional authorization bit a which indicates by a "1" that the sequence is authorized and by a "0"
that the sequence is forbidden. The forbidden and authorized sequences may also be differentiated by being stored in two distinct memory areas, one only containing authorized sequences, the other only containing forbidden sequences. A combination of both solutions may also be used, that is, a first memory area which only stores forbidden sequences and a second memory area which stores forbidden and authorized sequences differentiated by the state of an authorization bit.
Upon programming of a sequence, the authorization bit may be set to one state or the other according to the special symbol used to end the sequence To check whether a dialed number is or is not forbidden (at step 108), each stored sequence is compared with a corre-sponding number of the first digits of the dialed number. Among the sequences which coincide with the first digits of the dialed number, the longest will determine whether the number is or is not authorized.
Fig. 6 shows a detailed flowchart of a processing example implemented by the program of microcontroller 12 to achieve this aim. This flowchart actually corresponds to the operations which are performed at 108 in the flowchart of Fig. 5.
For this processing, each sequence is stored with its length in the RAM.
At 200, the dialed number is acquired. A general authorization flag A is set to 1. At 202, a variable Lmax is set to zero. This variable Lmax is used to contain the length of the longest sequence coinciding with the first digits of the dialed number.
At 204, in the list of stored sequences, the following sequence S, its length L, and its authorization bit a are read.
Of course, the sequence initially read at 204 is the first in the list.
At 206, it is checked whether the end of the sequence list is reached.
If the end of the list is not reached, it is checked at 108 whether the length L of the current sequence is strictly greater than length Lmax. If not, it is useless to continue and the next sequence is read at 204. Indeed, in this case, the sequence being ex~mine~ cannot be taken into account, since a longer sequence (of length Lmax) coinciding with the dialed number was previously found.
Conversely, if the length L of current sequence S is greater than Lmax, sequence S is compared at 210 to the dialed number truncated after L digits, that is, the L first digits of the dialed number are compared with the L digits of sequence S.
If they are not equal, the next sequence is read at 204. If they are equal, a coinciding sequence has been found which is longer than the coinciding sequences previously found. Thus, at 212, length Lm~x is assigned with the length L of the current sequence. Further, general authorization flag A is assigned with the authorization bit a of the current sequence. The next sequence is then read at 204.
When the end of the list of sequences is reached, step 206 is followed by a step 214 where the state of general authori-zation flag A is checked. If it is equal to 1, that is, if the longest coinciding sequence found is an authorized sequence, the processing ends with the passing from step 108 of Fig. 5 to step 110, where the telephone communication is carried on normally with the number which has been dialed.
If general authorization flag A is at 0, that is, if the longest coinciding sequence found is a forbidden sequence, the processing ends with the passing from step 108 of Fig. 5 to step 112 where switch K is opened to simulate an on-hook condition.
An access restriction device of the type of Fig. 1 may, according to the present invention, be completed by a dialing circuit included within circuitry 14. The device then has several useful applications.
A first application is a cost effective way for checking the program contents of the device. For this purpose, the manufacturer or retailer of the device may create a voice server whose teleph~n~ number is stored in the RAM. When the user dials a specific code, the device, through the dialing circuit, calls the voice server and then transmits the contents of the RAM
thereto by DTMF. The voice server will then pronounce in natural language all the digits and symbols stored in the RAM. It may even be designed to recognize the authorized and forbidden sequences and other information and say them as such. The telephone number of the voice server will of course be proyrdll~l~ble by the user.
This application avoids the use of complex additional circuitry (display, serial port...) for enabling the user to check the programming of the device.
Another application is to let the device perform an automatic call upon off-hook. This is particularly useful for children or persons unable to dial or remember a number.
For this purpose, the microprocessor is programmed to wait for a predetermined time interval after an off-hook. If, inside the time interval, no number is dialed, the microprocessor causes the dialing of a specific number stored in the RAM. If a number is dialed within the time interval, the device behaves in the normal way described hereabove.
Of course, the present invention is likely to have various alterations, modifications, and improvements which will readily occur to those skilled in the art. In particular, those skilled in the art may establish other flowcharts than those described to perform the desired functions. For example, instead of scanning the entire list of stored sequences in order to find the longest coinciding sequence, it can be provided that, upon programming the sequences to forbid or authorize, the program of the microcontroller reorganizes the sequences in the memory by decreasing lengths. Thus, in the flowchart corresponding to step 108 of Fig. 5, the sequences are simply successively read until a coinciding sequence is found. Then, the sequence which has just been found necessarily is the longest of the coinciding sequences and its authorization bit a determines whether the dialed number is or is not forbidden.
The present invention has been described in relation with a programmed microcontroller, but it may be implemented in hardware.
Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accord-ingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited CA 02227l89 l998-04-2l only as defined in the following claims and the equivalents thereto.
What is claimed is:
RA~K~ROUND OF l~E lNv~NllON
Field of the Invention The present invention relates to an access restriction device meant to prevent a telephone communication when a forbid-den number is dialed on a subscriber tel~ph~nP.
Discussion of the Related Art Fig. 1 schematically shows a conventional restriction5 device 8, of the type described in PCT patent application WO
95/12266. Device 8 includes a switch K connected to interrupt a telephonP line LT which is connected to a subscriber telephone 10. Switch K is controlled by a microcontroller 12 which receives signals from circuitry 14 for detecting, in particular, an off-hook condition and decoding the DTMF signals carried on line LT.Circuitry 14 is shown connected to line LT between switch K and telephone 10, but it could also be connected upstream of switch K, since it is not meant to operate when switch K is open.
Microcontroller 12 is associated with a ROM including the program to be executed by the microcontroller, and with a RAM
for storing the variables. The RAM stores in particular forbidden and authorized sequences of digits, pro~ r dll~l~ble by the user.
Microcontroller 12 and circuitry 14 are powered by a source 16 which takes the power available on telephone line LT
upstream of switch K.
Fig. 2 illustrates a main application of the access restriction device described in the above-mentioned PCT patent application. A simple telephone installation, especially at a private home, may include several telephone sets 10 connected to respective sockets 20. Teleph~nP sets 10, and thus sockets 20, are connected in parallel to the two wires of teleph~ne line LT.
Access restriction device 8 is connected, as shown, to the two wires which connect the first socket 20 of the instal-lation to an exchange 22. Thereby, device 8 can detect a forbidden sequence dialed from any of telephone sets 10 and interrupt the line supplying all the teleph~n~ sets.
A drawback of this installation is that the wires to which restriction device 8 is to be connected are not always reachable or easy to find, which usually requires the intervention of a professional. As a result, the cost of the installation is most often too high for a private person to be tempted to adopt it.
Of course, an access restriction device may be installed in other places, for example, between a telephone set and its socket. But then, the access restriction is avoided by just plugging another telephone set in the socket.
Summary of the invention An object of the present invention is to provide a telephon~ access restriction device which may easily be installed by a private person and which nevertheless protects an entire telephone installation.
This object is achieved by a tel~phon~ socket including two terminals for connection to two respective wires of a tele-phone line, including an access restriction device for preventing a tel~ph~ne communication upon dialing of a number beginning with a forbidden sequence of digits, the restriction device being connected to the two terminals and including a switch connected between a first one of the two terminals and an additional terminal, the two wires of the tel~phone line being respectively connected to the second one of the two terminals and to the additional terminal.
According to an embodiment of the invention, the access restriction device includes a memory freely programmable by a user to store forbidden sequences of digits; and analysis means connected to the line for acquiring the digits dialed on a telephone set, comparing them to the forbidden sequences stored in the memory and, in case of a coincidence, controlling the opening of the switch to simulate an on-hook.
According to an embodiment of the invention, the access restriction device becomes temporarily inoperative after the dialing on the tel~phonP set of a confidential code, this confidential code being differentiated from a telephone number by the dialing with the code of a first combination of special symbols.
According to an embodiment of the invention, the dialing of the confidential code causes an opening followed by a closing of the switch, the device becoming operative again upon a subsequent on-hook.
According to an embodiment of the invention, a sequence is proyLd~ ble in the memory via the telephone dial after dialing the confidential code with a second combination of special symbols.
According to an embodiment of the invention, the location of a sequence in the memory is identified by the dialing of a location number and of a specific combination of special symbols.
According to an embo~im~nt of the invention, the memory further stores authorized sequences of digits, the coincidence of a sequence with a forbidden number or an authorized number being indicated by an additional information associated with each sequence, the analysis means being adapted to find, among the stored sequences, the longest sequence coinciding with the dialed number, and to control or not the opening of the switch depending on the additional information of the found sequence.
According to an embodiment of the invention, the additional information associated with a sequence is an authorization bit stored with the sequence, this bit being set, upon a programming, by the dialing or not of a special symbol after the dialing of the sequence.
According to an embodiment of the invention, the memory includes a first area for storing forbidden sequences and a second area for storing authorized sequences, the additional information associated with a sequence being provided by the area in which the sequence is stored.
According to an embodiment of the invention, the second area is provided to further store forbidden sequences, the additional information associated with a sequence stored in the second area being supplied by an authorization bit stored with the sequence.
According to an embodiment of the invention, the sequence lengths are stored with the sequences.
According to an embodiment of the invention, the socket includes a cover attached by screws with non-standard drive recesses.
According to an embodiment of the invention, the restriction device includes a dialing circuit for dialing a specific number and then transmitting the contents of the memory through DTMF.
According to an embodiment of the invention, the restriction device includes a dialing circuit, the microprocessor being programmed to cause the dialing of a stored number when no number is dialed during a predetermined time interval after an off-hook.
The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.
Brief Description of the Drawinqs Fig. 1, previously described, schematically shows a conventional access restriction device;
Fig. 2, previously described, shows a conventional arrangement of an access restriction device in a simple tel~phon~
installation;
Fig. 3 shows an arrangement of a telephon~ socket according to the present invention, provided with an access restriction device, in a conventional telephone installation of the type of Fig. 2;
Fig. 4 shows an open perspective view of an embodiment of a telephone socket according to the present invention, provided with an access restriction device;
Fig. 5 shows a general flowchart of the operation of an access restriction device; and Fig. 6 shows an example of a flowchart for managing a list of forbidden and authorized numbers according to the present invention.
Detailed Description The present invention is based on the analysis of the specific way in which the sockets of a simple installation are connected to one another.
As shown in Fig. 2, a conventional telephone socket 20 includes two terminals 20-1 and 20-2 connected to contacts of the socket for cooperating with a plug of the corresponding teleph~n~
set 10. Further, terminals 20-1 and 20-2 of a socket are connected by two wires to terminals 20-1 and 20-2 of the preced-ing socket. The two wires of telephone line LT are connected to the two terminals 20-1 and 20-2 of the first socket 20.
According to the present invention, it is provided to place an access restriction device 8 in a conventional tel~phon~
socket, eventually modified to accommodate the restriction device.
Fig. 3 shows a socket 20' according to the present invention mounted in a conventional telephon~ installation.
Preferably, socket 20~ according to the present invention is the first one. This socket 20' includes, like a conventional socket, two terminals 20-1 and 20-2 for connection to a corresponding telephon~ set 10. Terminals 20-1 and 20-2 of socket 20' are connected conventionally by two wires to termin~ls 20-1 and 20-2 of the next socket 20. However, only terminal 20-1 of socket 20' is connected to a wire of telephone line LT. The rPm~ining wire of telephone line LT is connected to a terminal 20-3 which is a part of restriction device 8. Restriction device 8 is connected to terminals 20-1, 20-2, and 20-3 to constitute the arrangement of Fig. 1, switch K being connected between terminals 20-2 and 20-3. Access restriction device 8 then performs exactly the same function as that of Fig. 2, that is, it disconnects all telephone sets 10 from exchange 22 as soon as a forbidden sequence is dialed on any of the telephone sets.
An access restriction device included, according to the present invention, in a telephone socket 20' is particularly easy to install. Indeed, the first conventional socket 20 is just replaced by a socket 20' according to the present invention and the wires are reconnected to this socket like they were connected in the conventional socket, except for one of the wires coming from exchange 22, which is connected to terminal 20-3 of restriction device 8.
A user with little experience may make a mistake by swapping the wires which are connected to terminals 20-2 and 20-3. In this case, when a forbidden sequence is dialed, device 8 disconnects all telephone sets 10 except the one connected to the first socket 20'. This malfunction may easily be detected by the user, who will thereby swap the wires connected to terminals 20-2 and 20-3 to obtain the correct operation. This connection may, conversely, be voluntary if the telephone set connected to socket 20' is located in a room inaccessible to unauthorized users.
Of course, a socket 20' according to the present inven-tion may be used in an installation with a single telephone set.Terminal 20-2 is then not used.
Fig. 4 shows an open perspective view of an embodiment of socket 20l according to the present invention. As an example, this socket is a T-type socket used in France. Restriction device 8 is in the form of a printed circuit housed against one of the surfaces of a cover 40 of the socket.
Cover 40 is normally fixed to a base 42 by means of two screws. A person who would discover the function of the socket according to the present invention could easily dismount cap 40 and reestablish the unrestricted operation of the socket. To limit such a risk, the screws for fixing cover 40 to base 42 are preferably provided with non-st~n~rd drive recesses, for example triangular, so that only the owner of the corresponding screw-driver can dismount the cover.
To summarize, the operation of a restriction device 8 of the type of Fig. 1 and according to the present invention is the following. Microcontroller 12 is programmed to regularly check the output of off-hook detector 14. When an off-hook condition is detected, the microcontroller acquires any digit or symbol dialed on telPphon~ set 10 via DTMF decoder 14. If the digit acquired in this mAnn~r by the microcontroller corresponds to a forbidden sequence stored in the RAM, the microcontroller controls the opening of switch K during a time which is sufficiently long to be perceived as an on-hook by the exchange.
Two possibilities for controlling switch K may be devised. A first possibility is to imm~;ately open switch K upon detection of a forbidden number. A second possibility is to open switch K only after a predetermined time interval, which enables, instead of forbidding the communication, to limit the duration of this communication. Thus, a pro~ r dllll~ble maximum duration of communication could also be stored in the RAM, for each forbidden sequence. Of course, the counting down of such a duration pref-erably starts when the called telephone set hooks off. Conven-tional circuits to be included in circuitry 14 could detect such events.
The sequences are stored in the RAM during a program-ming phase described hereafter and entered by dialing a confidential code on the telephone dial.
Fig. 5 shows a more detailed general flowchart of the operations performed by the program of microcontroller 12.
At 100, the output of off-hook detector 14 is polled.
At 104, the sequence of symbols or digits dialed on telephone set 10 and provided to the microcontroller by DTMF decoder 14 is acquired. Here, two solutions are possible before proceeding with the next step 106. A first solution is to proceed with step 106 upon each acquisition of a new digit or symbol. A second solution consists in acquiring all the dialed symbols or digits before proceeding with step 106. The end of the dialing of a sequence is detected, for example, by the fact that the user pauses for a time longer than a predetermined delay, or else by the fact that a tone is detected on line LT indicating the ringing of the called telephone set.
At 106, it is checked whether the sequence corresponds to a confidential code stored in the RAM. To differentiate a confidential code from a normal number, the code is dialed, for example, by preceding and following it with special symbols, such as symbols * and #.
At 108, the dialed sequence does not contain a confi-dential code, or the confidential code is wrong. It is then checked whether the dialed sequence corresponds to a forbidden sequence stored in the RAM.
If the dialed sequence is not forbidden, or if it corresponds to a wrong confidential code, an on-hook is awaited at 110, that is, the tel~phone communication carries on conventionally with the numbers which were dialed, until the user hooks on. Of course, in the case where a wrong confidential code was dialed, no telephone communication is obtained, since a confidential code does not correspond to a telephone number.
Conversely, if the dialed sequence corresponds to a forbidden sequence at 108, microcontroller 12 controls the opening of switch K at 112 during a time sufficiently long to be interpreted as an on-hook by the exchange. Switch K is then closed again at 114.
After awaiting the on-hook condition at 110 or the closing of switch K at 114, the microcontroller starts waiting for a new off-hook condition at 100.
If the dialed sequence corresponds to a correct code at 106, it is checked at 116 whether the sequence starts with a specific special symbol, for example symbol #. If such is not the case, for example if the sequence begins with symbol *, an on-hook is caused at 118 by the opening of switch K. m e arrival at step 118 means that the user dialed a correct confidential code with a specific combination of special symbols indicating that all restrictions must be temporarily raised.
Switch K is closed again at 120. This causes a new off-hook, since the user is normally still holding the handset. The user then only has to dial the desired number, which will not be checked by steps 104 to 108. Any number is therefore authorized, even a normally forbidden number, and the communication is carried on normally until an on-hook condition is detected at 110 .
A confidential code is preferably inserted between two special symbols, the beginning symbol indicating a confidential code, and the end symbol indicating the end of the confidential code. As a result, the code can have any number of digits.
Preferably, two-digit confidential codes which may correspond to France Telecom services will be avoided.
Of course, the forbidden sequences as well as the confidential code and other information should be programmable.
The user expresses the desire of programming by preceding his confidential code with a specific special symbol, for example symbol # in the present example (symbol * being used to raise restrictions). Then, step 116 is followed by a programming mode at 122.
In the programming mode, various techniques may be used to input the forbidden sequences in the RAM as well as a variety of associated information. For example, a memory location is identified by a two-digit number framed by special symbols, followed by the forbidden sequence, then by a special symbol to indicate the end of the sequence. The confidential code, so that it can be modified, is stored at a specific location accessible in the same way as the locations containing forbidden sequences.
Of course, the confidential code is factory set to a specific value and provided to the user in the user m~nl]~1.
Once the user has performed his programming, he hangs up the handset, which ends the programming mode at 110.
In the flowchart of Fig. 5, the sequences stored in the RAM have been considered as forbidden sequences. A specific stored sequence forbids the calling of any number which starts with this sequence. Thus, by storing longer or shorter sequences, families of forbidden numbers are defined. For example, in many countries, by storing sequence 00, the calling of any number abroad is forbidden. The storing of sequence 36 forbids, in France, the use of Minitel services. Of course, a sequence may correspond to a complete number.
A disadvantage of only storing forbidden sequences with a small number of digits is that large families of forbidden numbers are defined, which may contain numbers which one may want to use.
To avoid this disadvantage, the present invention provides to also store authorized sequences to define sub-families of authorized numbers within families of forbidden numbers. Then, for example, by storing sequence 36 as forbidden and sequence 3611 as authorized, the calling of any number start-ing with 36 is forbidden, except for 3611 (and any other number beginning with 3611).
Authorized sequences are differentiated from forbidden sequences by additional information. For example, each sequence may be stored with an additional authorization bit a which indicates by a "1" that the sequence is authorized and by a "0"
that the sequence is forbidden. The forbidden and authorized sequences may also be differentiated by being stored in two distinct memory areas, one only containing authorized sequences, the other only containing forbidden sequences. A combination of both solutions may also be used, that is, a first memory area which only stores forbidden sequences and a second memory area which stores forbidden and authorized sequences differentiated by the state of an authorization bit.
Upon programming of a sequence, the authorization bit may be set to one state or the other according to the special symbol used to end the sequence To check whether a dialed number is or is not forbidden (at step 108), each stored sequence is compared with a corre-sponding number of the first digits of the dialed number. Among the sequences which coincide with the first digits of the dialed number, the longest will determine whether the number is or is not authorized.
Fig. 6 shows a detailed flowchart of a processing example implemented by the program of microcontroller 12 to achieve this aim. This flowchart actually corresponds to the operations which are performed at 108 in the flowchart of Fig. 5.
For this processing, each sequence is stored with its length in the RAM.
At 200, the dialed number is acquired. A general authorization flag A is set to 1. At 202, a variable Lmax is set to zero. This variable Lmax is used to contain the length of the longest sequence coinciding with the first digits of the dialed number.
At 204, in the list of stored sequences, the following sequence S, its length L, and its authorization bit a are read.
Of course, the sequence initially read at 204 is the first in the list.
At 206, it is checked whether the end of the sequence list is reached.
If the end of the list is not reached, it is checked at 108 whether the length L of the current sequence is strictly greater than length Lmax. If not, it is useless to continue and the next sequence is read at 204. Indeed, in this case, the sequence being ex~mine~ cannot be taken into account, since a longer sequence (of length Lmax) coinciding with the dialed number was previously found.
Conversely, if the length L of current sequence S is greater than Lmax, sequence S is compared at 210 to the dialed number truncated after L digits, that is, the L first digits of the dialed number are compared with the L digits of sequence S.
If they are not equal, the next sequence is read at 204. If they are equal, a coinciding sequence has been found which is longer than the coinciding sequences previously found. Thus, at 212, length Lm~x is assigned with the length L of the current sequence. Further, general authorization flag A is assigned with the authorization bit a of the current sequence. The next sequence is then read at 204.
When the end of the list of sequences is reached, step 206 is followed by a step 214 where the state of general authori-zation flag A is checked. If it is equal to 1, that is, if the longest coinciding sequence found is an authorized sequence, the processing ends with the passing from step 108 of Fig. 5 to step 110, where the telephone communication is carried on normally with the number which has been dialed.
If general authorization flag A is at 0, that is, if the longest coinciding sequence found is a forbidden sequence, the processing ends with the passing from step 108 of Fig. 5 to step 112 where switch K is opened to simulate an on-hook condition.
An access restriction device of the type of Fig. 1 may, according to the present invention, be completed by a dialing circuit included within circuitry 14. The device then has several useful applications.
A first application is a cost effective way for checking the program contents of the device. For this purpose, the manufacturer or retailer of the device may create a voice server whose teleph~n~ number is stored in the RAM. When the user dials a specific code, the device, through the dialing circuit, calls the voice server and then transmits the contents of the RAM
thereto by DTMF. The voice server will then pronounce in natural language all the digits and symbols stored in the RAM. It may even be designed to recognize the authorized and forbidden sequences and other information and say them as such. The telephone number of the voice server will of course be proyrdll~l~ble by the user.
This application avoids the use of complex additional circuitry (display, serial port...) for enabling the user to check the programming of the device.
Another application is to let the device perform an automatic call upon off-hook. This is particularly useful for children or persons unable to dial or remember a number.
For this purpose, the microprocessor is programmed to wait for a predetermined time interval after an off-hook. If, inside the time interval, no number is dialed, the microprocessor causes the dialing of a specific number stored in the RAM. If a number is dialed within the time interval, the device behaves in the normal way described hereabove.
Of course, the present invention is likely to have various alterations, modifications, and improvements which will readily occur to those skilled in the art. In particular, those skilled in the art may establish other flowcharts than those described to perform the desired functions. For example, instead of scanning the entire list of stored sequences in order to find the longest coinciding sequence, it can be provided that, upon programming the sequences to forbid or authorize, the program of the microcontroller reorganizes the sequences in the memory by decreasing lengths. Thus, in the flowchart corresponding to step 108 of Fig. 5, the sequences are simply successively read until a coinciding sequence is found. Then, the sequence which has just been found necessarily is the longest of the coinciding sequences and its authorization bit a determines whether the dialed number is or is not forbidden.
The present invention has been described in relation with a programmed microcontroller, but it may be implemented in hardware.
Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accord-ingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited CA 02227l89 l998-04-2l only as defined in the following claims and the equivalents thereto.
What is claimed is:
Claims (14)
1. A telephone socket (20') including two terminals (20-1, 20-2) for connection to two respective wires of a telephone line (LT), including an access restriction device (8) for preventing a telephone communication upon dialing of a number beginning with a forbidden sequence of digits, the restriction device being connected to the two terminals and including a switch (K) connected between a first one (20-2) of the two terminals and an additional terminal (20-3), the two wires of the telephone line being respectively connected to the second one of the two terminals (20-1) and to the additional terminal.
2. The socket of claim 1, wherein the access restriction device (8) includes:
- a memory (RAM) freely programmable by a user to store forbidden sequences of digits; and - analysis means (12, 14) connected to the line for acquiring the digits dialed on a telephone set, comparing them to the forbidden sequences stored in the memory and, in case of a coincidence, controlling the opening of the switch to simulate an on-hook.
- a memory (RAM) freely programmable by a user to store forbidden sequences of digits; and - analysis means (12, 14) connected to the line for acquiring the digits dialed on a telephone set, comparing them to the forbidden sequences stored in the memory and, in case of a coincidence, controlling the opening of the switch to simulate an on-hook.
3. The socket of claim 2, wherein the access restriction device becomes temporarily inoperative after the dialing on the telephone set of a confidential code, this confidential code being differentiated from a telephone number by the dialing with the code of a first combination of special symbols (*).
4. The socket of claim 3, wherein the dialing of the confidential code causes an opening followed by a closing of the switch, the device becoming operative again upon a subsequent on-hook.
5. The socket of claim 3, wherein a sequence is programmable in the memory via the telephone dial after dialing the confidential code with a second combination of special symbols (#).
6. The socket of claim 5, wherein the location of a sequence in the memory is identified by the dialing of a location number and of a specific combination of special symbols.
7. The socket of any of claims 2 to 6, wherein the memory (RAM) further stores authorized sequences of digits, the coincidence of a sequence with a forbidden number or an authorized number being indicated by an additional information (a) associated with each sequence, the analysis means (12) being adapted to find, among the stored sequences, the longest sequence coinciding with the dialed number, and to control or not the opening of the switch (K) depending on the additional information of the found sequence.
8. The socket of claim 7, wherein the additional information associated with a sequence is an authorization bit (a) stored with the sequence, this bit being set, upon a programming, by the dialing or not of a special symbol after the dialing of the sequence.
9. The socket of claim 7, wherein the memory (RAM) includes a first area for storing forbidden sequences and a second area for storing authorized sequences, the additional information associated with a sequence being provided by the area in which the sequence is stored.
10. The socket of claim 9, wherein the second area is provided to further store forbidden sequences, the additional information associated with a sequence stored in the second area being supplied by an authorization bit (a) stored with the sequence.
11. The socket of any of claims 7 to 10, wherein the sequence lengths (L) are stored with the sequences.
12. The socket of claim 1, including a cover (40) attached by screws with non-standard drive recesses.
13. The socket of claim 2, wherein the restriction device includes a dialing circuit for dialing a specific number and then transmitting the contents of the memory through DTMF.
14. The socket of claim 2, wherein the restriction device includes a dialing circuit, the microprocessor being programmed to cause the dialing of a stored number when no number is dialed during a predetermined time interval after an off-hook.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR97/00692 | 1997-01-17 | ||
| FR9700692A FR2758678B1 (en) | 1997-01-17 | 1997-01-17 | ACCESS RESTRICTION DEVICE FOR TELEPHONE SET |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2227189A1 true CA2227189A1 (en) | 1998-07-17 |
Family
ID=9502910
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2227189 Abandoned CA2227189A1 (en) | 1997-01-17 | 1998-01-16 | Access restriction device for a telephone set |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0854623A1 (en) |
| JP (1) | JPH10229443A (en) |
| CA (1) | CA2227189A1 (en) |
| FR (1) | FR2758678B1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2389737B (en) * | 2002-06-01 | 2004-06-16 | Rory Joseph Donnelly | A telecommunications security unit |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2086187A (en) * | 1980-10-09 | 1982-05-06 | Standard Telephones Cables Ltd | Toll barring |
| GB2123254A (en) * | 1982-05-14 | 1984-01-25 | Answercall Limited | Telephone instruments |
| US5471524A (en) * | 1992-09-15 | 1995-11-28 | Donald G. Colvin | Toll call restrictor method and apparatus |
| FR2706682B1 (en) * | 1993-06-16 | 1995-07-21 | Mars Actel | Subscriber termination device. |
| CA2174956C (en) * | 1993-10-28 | 2002-09-24 | Eric Timothy Smith | Telephone bar device |
-
1997
- 1997-01-17 FR FR9700692A patent/FR2758678B1/en not_active Expired - Fee Related
-
1998
- 1998-01-16 EP EP98410002A patent/EP0854623A1/en not_active Withdrawn
- 1998-01-16 CA CA 2227189 patent/CA2227189A1/en not_active Abandoned
- 1998-01-19 JP JP10020147A patent/JPH10229443A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2758678B1 (en) | 1999-04-16 |
| FR2758678A1 (en) | 1998-07-24 |
| EP0854623A1 (en) | 1998-07-22 |
| JPH10229443A (en) | 1998-08-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |