IL107096A - Telephone call filtering device - Google Patents

Description

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C. 91331 FIELD OF THE INVENTION This invention relates to telephone answering systems.

BACKGROUND OF THE INVENTION The telephone is a mixed blessing. On the one hand, it enables us to communicate with people all over the world; but on the other hand, it is a frequent cause of disturbance and can be most irksome. Nowadays, it is becoming increasingly popular for market research organizations and the like to perform telephone polls and the general, widespread use of the telephone inevitably means that telephone subscribers are increasingly bothered by all sorts of people with whom they have no interest in talking. Even apart from this, telephone calls can be mis-dialled or mis-routed resulting in people being disturbed unnecessarily, sometimes even in the small hours of the morning. Yet a further consideration is the unfortunate use of the telephone to frighten or threaten vulnerable people, a practice which has led more than one subscriber to change his or her telephone number and even to go ex-directory.

Such a drastic solution is also used by many professional people who work sufficiently long hours in their offices without wishing also to be disturbed at home. Many of these people also go ex-directory so that their name is not listed in the telephone directory and is also not communicated by the telephone company to people using the directory enquiry service.

The major drawback with such an approach is that it is an all or nothing solution. In other words, there is no way to be ex-directory so far as some people are concerned but not others.

Conventional telephone answering services have come some way to solving the above dilemma. In effect, it is possible using such systems to receive all incoming calls, to listen to the caller and then to pick up the telephone only if it be desired to make contact. However, this demands that the user of such systems constantly monitors incoming calls because she or he, and not the answering system, is in effect the filter by means of which unwanted calls are filtered out.

It would clearly be desirable to provide such a filter wherein the telephone owner does not need to monitor incoming calls himself; which provides the security of going ex-directory without actually doing so; and yet which is sufficiently versatile to permit callers to make contact if it is absolutely essential that such contact be made; all without requiring monitoring by the user himself.

SUMMARY OF THE INVENTION It is an object of the invention to provide a telephone call filtering device in which the above requirements are realized.

According to the invention there is provided a telephone call filtering device, comprising a call filtering circuit energized by a source of d.c. electric power, the call filtering circuit including: a line input means for coupling to a telephone line belonging to a local subscriber, a telephone output means for coupling to a local tone dialling telephone belonging to the local subscriber, a ring detection means coupled to the line input means for generating a detection signal responsive to a remote subscriber telephon-ing the local subscriber, a password encoding means for encoding a local subscriber password, a voice module switchably coupled to the line input means and to the ring detection means and responsive to the detection signal for prompting the remote subscriber to enter the local subscriber's password, a password decoding means switchably coupled to the line input means for decoding a password transmitted by the remote subscriber, a first switching means coupled to the line input means and to the ring detection means and responsive to the detection signal for coupling the line input means to both the password decoding means and to the voice module, a password verification means coupled to the password encoding means and to the password decoding means for generating an accept signal if the transmitted password conforms to the local subscriber's password, respective ringing means coupled to the password verification means, to the line input means and to the telephone output means and responsive to the accept signal for sending respective ringing signals to the local telephone and to a remote telephone belonging to the remote subscriber, an answering detection means coupled to the telephone output means and responsive to the local subscriber lifting the receiver of the local telephone for generating an answering signal and for disabling the ringing means, and a second switching means coupled to the answering detection means and responsive to the answering signal for connecting the line input means to the telephone output means.

Preferably, in addition to providing a complete override whereby the device may be bypassed, there are also provided two passwords and correspondingly different messages: one of which is secret and known only to the user and those subscribers to whom he wishes to communicate it and the other of which is actually communicated as part of the message. By such means, the system permits in a first mode of operation only those subscribers who know the secret password to effect contact; whilst in a second mode of operation, it is left to the discretion of the caller whether his call is of sufficient importance to enter the password and thereby effect the desired communication.

BRIEF DESCRIPTION OF THE DRAWING In order to understand the invention and to see how the same may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawing, in which: Figs, la and lb are together a block diagram of the invention showing the principal functional components thereof.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In Figs, la and lb which have been separated for reasons of clarity but are to be read together, there is shown a device depicted generally as 10 comprising line input means 11a and lib for coupling to a telephone line 11 belonging to a local subscriber and telephone output means 12a and 12b for coupling to a local dual-tone multifrequency (DTMF) dialling telephone 12 belonging thereto. Coupled to the line input means 11a and lib is a ring detection means 13 connected to a timer 14 for generating a detection signal consequent to a remote subscriber telephoning the local subscriber. The timer 14 is coupled to a voice module 15 as well as to a relay 16 which constitutes a first switching means and is responsive to the detection signal provided by the ring detection means 13 for coupling the line input means 11 to the voice module 15 and to a password decoding means 17.

Thus, when the relay 16 is in the de-energized state, the line input means 11a and lib are respectively connected to floating relay contacts 16a and 16b, whilst when the relay 16 is energized by the detection signal, the line input means 11a and lib are respectively connected to relay contacts 16c and 16d which, in turn, are connected via a transformer 18 to the decoding means 17.

The timer 14 operates for a predetermined time interval, typically 30 seconds, during which time the relay 16 operates to connect the line input means 11a and lib to both the voice module 15 and to the password decoding means 17. At the end of the pre-set time interval, the relay 16 reverts to its normal position, wherein the line input means 11a and lib are disconnected from the voice module 15 and the password decoding means 17.

One or more passwords may be set by the local subscriber by means of a password encoding means 19, typically constituted by an array of dual-in-line (DIP) switches, for pre-setting one or more passwords each having typically three digits.

A password verification means 20 is coupled to the password encoding means 19 and to the password decoding means 17 for generating an accept signal if a password transmitted by the remote subscriber conforms to a local subscriber's password encoded by the password encoding means 19. A ringing means 21 is coupled to the password verification means 20 and via respective contacts 22a, 22b and 23a, 23b of a pair of relays 22 and 23 to the telephone output means 12a and 12b. The ringing means 21 is responsive to the accept signal for sending an intermittent 60 V ringing signal to the local telephone so as to operate its bell in order that the local subscriber may be aware of an incoming call.

The relay 23 constitutes a combined power failure indication and override means for connecting the telephone 12 directly to the line 11 in the event of a mains power failure. Thus, the relay 23 is connected to a 12 V d.c. power supply 24 which is typically fed from an a.c. mains supply outlet via a suitable transformer and regulator (not shown). On supplying power to the relay 23, the contacts 23a and 23b are respectively connected to the telephone output means 12a and 12b. In the event of power failure, the telephone output means 12a and 12b are respectively connected to a pair of contacts 23c and 23d of the relay 23, which are respectively connected directly to the line input means 11a and to the line input means lib through a resistor 26.

Between each ringing signal, the relay 22 is energized by the ringing means 21 for connecting the contacts ,23a and 23b of the relay 23 to the contacts 22a and 22b of the relay 22, whereby between successive ringing signals the telephone 12 is connected to the ringing means 21 for producing an audible ring. Likewise, the voice module 15 is coupled to the password verification means 21 and is itself responsive to the accept signal generated thereby for generating a ringing tone which is fed to the line input means 11a and lib so as to be heard by the remote subscriber. In this way, even though the local telephone 12 is, as yet, completely isolated from the telephone line 11, the remote subscriber still hears the dialling tone as if it had been generated by the local telephone.

A timing means 25 is coupled to the password verification means 20 for disabling the accept signal after a predetermined time interval in order that the respective ringing means 15 and 21 are likewise disabled and do not ring continuously in the event that the local subscriber does not answer and the remote subscriber does not hang up.

An answering detection means 27 connected across the resistor 26 is responsive to the local subscriber lifting the receiver of the local telephone for generating an answering signal and the password verification means 20 is coupled to the answering detection means 27 and is responsive to the answering signal so as to reset the accept signal and thereby disable the ringing means constituted by the voice module 15 and the ringing means 21. A relay 28 (constituting a second switching means) is coupled to the answering detection means 27 and is responsive to the answering signal generated thereby for connecting respective relay contacts 28a and 28b to respective relay contacts 22c and 22d of the relay 22. Thus, when the relay 28 is energized by the answering signal and the relay 23 is energized, the line input means 11a and lib are connected via the contacts 28a, 22c and 23a and the contacts 28b, 22d and 23b to the telephone output means 12a and 12b whereby the local telephone is connected directly to the line 11, permitting communication between the local and remote subscribers.

A second pair of relay contacts 28c and 28b are respectively connected to the 12 V d.c. power supply 24 and to the answering detection means 27. Thus, when the relay 28 is de-energized and the relay 23 is energized, the telephone output means 12a is connected via relay contacts 23a, 22c and 28c to +12 V d.c whilst the telephone output means 12b is connected via relay contacts 23b, 22d and 28d to the answering detection means 27. When the telephone receiver is now lifted, the 12 V d.c. supply is applied across the telephone which functions a simple impedance, the resulting current being detected by the answering detection means 27 and providing an indication that the receiver has been lifted. The resulting answering signal generated by the answering detection means 27 energizes the relay 28, whereby its contacts 28a and 28b are respectively connected to the telephone output means 12a and 12b, thereby connecting the telephone output means 12a and 12b to the line input means 11a and lib respectively.

If desired, more than one password encoding means may be provided each for encoding a corresponding password and a mode selection means 30 coupled to the password verification means 20 is thereby coupled to the password encoding means 18 and to the voice module 15 for selecting one of the passwords and the appropriate message. In such a configuration one password may be a secret password known only to the local subscriber and those particular associates whom she or he wishes to know the password; whilst the other password may actually be communicated as part of the corresponding voice message. Thus, in a first mode of operation employing the secret password, only those remote subscribers who know the secret password are able to effect communication. In a second mode of operation, where the secret password is actually communicated as part of the voice message, it is left to the discretion of the caller as to whether the call is sufficiently important to warrant interrupting the local subscriber. If so, then the caller need merely enter the password communicated as part of the voice message, whereupon the password verification means will ultimately ensure that a connection is established.

Likewise, the mode selection means 30 may include an override whereby the device is effectively bypassed, the line input means 11 being permanently connected to the telephone output means 12a and 12b.

In the event of a power failure, the relay 23 will cease to be energized and the telephone output means 12a and 12b are connected directly via the respective relay contacts 23c and 23d to the line input means 11a and lib. In this way, the telephone 12 is permanently connected to the line 11 for receiving and making calls as normal even during a power failure.

It should be noted that the invention is suitable for use with dual-tone multifrequency (DTMF) type telephones, the decoding means 17 being responsive to the received tones for decoding the password. The password itself is transmitted simply by dialling the required digits which, in a pushbutton type telephone, is accomplished by pressing the appropriate pushbuttons.

Thus, the invention provides a versatile telephone call filtering device whereby a subscriber may, effectively, become ex-directory or alternatively may leave it to the discretion of a caller as to whether his or her call is really important enough to warrant interruption. In either case, no local monitoring by the subscriber is required.

Claims (9)

CLAIMS:

1. A telephone call filtering device, comprising a call filtering circuit energized by a source of d.c. electric power, the call filtering circuit including: a line input means for coupling to a telephone line belonging to a local subscriber, a telephone output means for coupling to a local tone dialling telephone belonging to the local subscriber, a ring detection means coupled to the line input means for generating a detection signal responsive to a remote subscriber telephoning the local subscriber, a password encoding means for encoding a local subscriber password, a voice module switchably coupled to the line input means and to the ring detection means and responsive to the detection signal for prompting the remote subscriber to enter the local subscriber's password, a password decoding means switchably coupled to the line input means for decoding a password transmitted by the remote subscriber, a first switching means coupled to the line input means and to the ring detection means and responsive to the detection signal for coupling the line input means to both the password decoding means and to the voice module, a password verification means coupled to the password encoding means and to the password decoding means for generating an accept signal if the transmitted password conforms to the local subscriber's password, respective ringing means coupled to the password verification means, to the line input means and to the telephone output means and responsive to the accept signal for sending respective ringing signals to the local telephone and to a remote telephone belonging to the remote subscriber, an answering detection means coupled to the telephone output means and responsive to the local subscriber, lifting the receiver of the local telephone for generating an answering signal and for disabling the ringing means, and a second switching means coupled to the answering detection means and responsive to the answering signal for connecting the line input means to the telephone output means.

2. The device according to Claim 1, wherein the password encoding means is a dual-in-line switch comprising a plurality of switch elements each in respect of a decimal digit.

3. The device according to Claim 1, further including timing means coupled to the ring detection means for disabling the ring detection means after a predetermined period of time whereby the remote subscriber must transmit the local subscriber's password within said predetermined period of time.

4. The device according to Claim 1, wherein: the password encoding means encodes more than one password, the voice module produces different message prompts each in respect of a corresponding one of the encoded passwords, and there is further provided a mode selection means coupled to the password encoding means for selecting one of the encoded passwords and to the voice module for producing the corresponding message.

5. The device according to Claim 4, wherein the mode selection means includes override means for connecting the line input to the telephone output.

6. The device according to Claim 4, wherein: the voice module produces different messages in respect of each encoded password, and there is further provided a message selection means coupled to the voice module for selecting one of said message in respect of each one of the encoded passwords.

7. The device according to Claim 1, further including a timing means coupled to the password verification means for disabling the accept signal after a predetermined time interval.

8. The device according to Claim 1, wherein: the source of d.c. electric power is derived from a mains electricity supply, a power failure indication means is provided for providing a power failure indication signal consequent to an interruption of the mains electricity supply, and an override means is provided coupled to the power failure indication means and responsive to the power failure indication signal for connecting the line input means directly to the telephone output means.

9. A method for using the device according to Claim 4, comprising the steps of: (a) encoding two different passwords with the password encoding means, (b) storing corresponding messages in the voice module one prompting the remote subscriber to enter a secret password and the other informing the remote subscriber of the password but requesting that he enter said password in emergency only, (c) selecting one of the encoded passwords arid the corresponding message, (d) receiving a password transmitted by the remote subscriber, (e) comparing the received password with the encoded password selected in step (c), and (f) if the received password matches the encoded password selected in step (c), connecting the line input means to the telephone output means. For the Applicants, LD COHN AND PARTNERS 91331spc.jt/prg/jjt/22.9.1993