WO2002030092A1

WO2002030092A1 - Apparatus and method for detecting inoperable and line busy conditions on telephone lines

Info

Publication number: WO2002030092A1
Application number: PCT/SG2001/000201
Authority: WO
Inventors: Eng Heng Ng
Original assignee: Eng Heng Ng
Priority date: 2000-10-06
Filing date: 2001-10-04
Publication date: 2002-04-11
Also published as: AU2001294501A1

Abstract

The present invention relates to the detection of inoperable and line busy conditions on telephone lines. It relates to the detection of open-circuits or short circuits between the telephone exchange and the telephone receiver or at the receiver and to alerting the subscriber to take corrective action. It also relates to the detection of line busy conditions for individual users across one common line so that any user can identify that the line is being used. Apparatus for connection to the telephone line includes detection means (3) to detect the presence of a low voltage on the telephone line; alarm means (12) to alert the user in response to detection of such a low voltage; and a line busy voltage detection means to detect the line busy signal and indicate the user that the line is being engaged.

Description

APPARATUS AND METHOD FOR.PETECTING INOPERABLE AND LINE BUSY

CONDITIONS ON TELEPHONE LINES

FIELD OF THE INVENTION

The present invention relates to the detection of in-operable and line busy conditions on telephone lines. It relates to the detection of open-circuits or short circuits between the telephone exchange and the telephone receiver or at the receiver and to alerting the subscriber to take corrective action. It also relates to the detection of line busy conditions for individual users across one common line so that any user can identify that the line is being used.

BACKGROUND OF THE INVENTION

It is a common practice to connect telephones in parallel to different locations in a building, for convenience and reduced costs, to just a single line of a telephone service provider. If any one of these parallel telephones is left in the "off-hook" position, no incoming call can be received until such condition is corrected.

In such a condition, the subscriber may only find about the "off-hook" condition, if at all, when he attempts to make a telephone call. Otherwise, for hours the subscriber may not receive incoming calls until such a faulty condition is corrected. He may then only find out when someone tells him that he could not get through.

It is also possible that one of the telephones has become faulty and has caused a short- circuit to the incoming telephone line, thus making it impossible to receive incomi. ,_b -^jails. There is nothing available to alert the subscriber of such a condition. He only knows about when he tries to make a call or if someone complains.

It is also possible that a telephone line gets open-circuited or short-circuited (i.e., it is "dead") somewhere between the telephone exchange and the subscriber's telephone point. Again the subscriber only finds out about it if he tries to make a call or someone tells him. In the above situations, it is frustrating for a caller not being able to get through to the desired subscriber. It may also be frustrating for the subscriber, not being able to call out. At best it is only inconvenient but in times of emergencies, these situations could have large repercussions.

Additionally when several telephone receivers use a line in parallel using a common line in parallel, then if one user is using the telephone, other users may not know unless they lift up the receiver and hear someone on the line. In such incidents it is a nuisance for the first user using the line when one of the other user picks up the telephone receiver. There is no means in existing telephone receivers connected in parallel to a line to indicate that the line is being used by some one.

Singapore patent number 69167 describes the detection of busy signals generated by a telephone exchange. These are generated when a caller, calling out, calls a number that is already in use, when the phone is left off the hook for more than a short period or when there is a partial short circuit in the line or telephone, equivalent to being left off the hook. It only monitors the busy signal tone and once the busy signal has continued for a certain period of time, causes a buzzer to sound or a light to flash to inform the user.

Whilst this overcomes some of the problems with telephones, it does not cure all the ones mentioned above.

It is the aim of the present invention to detect at least certain inoperable conditions of a telephone or a telephone line and then alleviate, at least partially, some of the above mentioned problems. The invention additionally aims in detecting line busy conditions in receivers, when one of the receiver connected parallel is engaged.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided apparatus for connection to a telephone line, comprising: detecting means for detecting the presence of a low voltage on said telephone line; and alarm means to be activated by an alarm activation signal from said detecting means in response to detection of a low voltage by said detection means.

According to a second aspect of the present invention, there is provided apparatus for connection to a telephone line, comprising: detecting means for detecting an open or short-circuit on said telephone line; and alarm means to be activated by an alarm activation signal from said detecting means when an open or short-circuit is detected by said detection means.

The detecting means is preferably operable to detect a low voltage corresponding to an open or short circuit, even when it is due to a fault on the line or to a fault in equipment connected to the line.

The detecting means advantageously may further comprise switch means operable to supply power to said alarm means when the voltage drops below a first predetermined value. For instance when the first predetermined voltage is a voltage corresponding to a voltage when a telephone on said line is no longer on the hook.

The detecting means may also be operable to activate said alarm means when the detected voltage drops below a second predetermined value. For instance when said second predetermined voltage is a voltage corresponding to a voltage when there is an open or siiort circuit on the line.

The apparatus may be operable to be powered by a rechargeable battery and further comprise a battery charging circuit to charge said rechargeable battery, advantageously using power from the telephone line.

Additionally, said detecting means may further comprise a second detector means to detect an "off-hook" condition of a telephone on said telephone line. An exemplary arrangement includes a busy tone detection means for comparing properties of an incoming signal with predetermined values to determine if the incoming signal is or contains a busy tone signal, for sending an activation signal to the alarm means. The busy tone detection means comprises a waveform converter for converting an analogue busy tone signal into a digital pulse signal and is operable on the basis that said busy tone signal includes signal bursts of a predetermined duration and said digital pulse signal is of the same duration.

In these aspects the alarm means may usefully comprise delay timer means for preventing activation of said alarm means, unless and until the alarm activation signal lasts at least a predetermined length of time.

Preferably too the apparatus further comprises second switch means to prevent operation when the apparatus is not connected to said telephone line. This can be manual and/or automatic, switching said apparatus ON when said apparatus is plugged into a socket and OFF when said apparatus is unplugged from said socket.

According to a third aspect of the present invention, there is provided a method of detecting in-operable conditions on a telephone line, comprising: detecting the presence of a low voltage on said telephone line; providing an alarm activation signal when said low voltage is detected; and activating an alert in response to an alarm activation signal.

According to a fourth aspect of the present invention, there is provided a method of detecting in-operable conditions on a telephone line, comprising: detecting the presence of an open or short-circuit on sajd telephone line; providing an alarm activation signal when said open or short-circuit is received; and activating an alert in response to said alarm activation signal.

Said detecting step preferably comprises detecting a low voltage corresponding to an open or short circuit.

It may include the step of supplying power to allow said alert to be activated when the detected voltage drops below a first predetermined value and the step of providing said alarm activation signal when the detected voltage drops below a second predetermined value. Advantageously, said alert activation step may include the step of preventing the activation of the alert unless and until the alarm activation signal lasts at least a predetermined length of time.

According to a fifth aspect of the invention there is provided an apparatus for connection to a telephone line, comprising: detecting means for detecting a line busy signal on said telephone line; and indicator means to be activated by the detection means in response to detection of a line busy signal by said detection means.

The apparatus may have said line busy signal resulting from detection of a reduced voltage on a line. Apparatus may further comprise a bridge rectifier to supply DC supply voltage to said indicator means.

The apparatus may comprise an LED as an indicator means which may be located within the telephone receiver unit.

According to the sixth aspect of the invention there is provided a method of indicating if a telephone line is busy, comprising: detecting a line busy signal on said telephone line; providing an activation signal when the line busy signal is detected; and using said activation signal to activate an indicator that the line is busy.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be further described by way of non-limitative example with reference to the accompanying drawings, in which:

Figure 1 is the block diagram of a preferred embodiment of this invention; Figure 2 is the waveform of one example of a telephone exchange signal; and Figure 3 is the waveform of another example of a telephone exchange signal. Figure 4 is the block diagram of a second embodiment of this invention. Figure 5 is the block diagram of a third embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a preferred embodiment of an apparatus for detecting in-operable conditions of telephone equipment and telephone lines.

An incoming telephone line is connected to a bridge polarity guard (1), which is a full wave bridge rectifier circuit and operates independently of the telephone line polarity. It also provides power to a battery charging circuit (2) and. provides a line voltage to a line voltage detector (3) and an AC coupler (5).

The battery charging circuit (2) provides a small charge to a rechargeable battery (14). The battery runs the apparatus and, in case the line is open or short circuited, the apparatus still functions from the battery power.

The line voltage detector (3) is connected to the bridge polarity guard (1). It includes a voltage divider network which detects the line voltage, particularly "on-hook" or "off-hook", line open or short circuit voltages by determining the voltage. It has two outputs, one high if the voltage is above 30V and the other high if it is below 2V. The >30V high line works in conjunction with a logic circuit to switch "on" power to the rest of the circuitry by means of a DC supply switch (4).

The DC supply switch (4) turns "on" the DC supply from the battery (14) to the rest of the circuitry according to a signal from the line voltage detector (3) (i.e., when the telephone line voltage drops below 30V) indicating a "off-hook" condition or worse. This switch is a reed relay type switch, which mechanically operates to open the supply line from the battery. If the phone is not "off-hook" this switch will be open to conserve the battery power.

The AC coupler (5), also connected to the bridge polarity guard (1), takes an incoming signal and blocks the DC component allowing only AC signals (i.e., audio, tone and noise) to pass through. A busy tone frequency filter (6) filters the signal from the AC coupler (5) to allow only a frequency or frequencies which are present in a busy tone through to an audio amplifier (7) which amplifies the weak busy tone frequency signal for further operations.

A waveform converter (8) then converts the analogue amplified signal to ON/OFF pulses, according to the length of the or any busy tone frequency signals within its incoming signal.

A busy tone detector (9) detects the length of the ON/OFF pulses from the waveform converter (8) and compares them with the waveform for the timings of a busy tone. If, thereby, a busy tone is determined to be present, it outputs a "true" logic signal to a delay timer (10).

The delay timer (10) prevents a false alarm being generated by the apparatus in the event when the subscriber calls into an engaged number which will, in turn, cause the telephone exchange to generate a busy tone back to the calling subscriber. In such occurrence, without the delay timer circuit (10), the apparatus will detect a busy tone and will trigger the alarm as though the telephone was in the "off-hook" position and not in use. The delay timer (10) has two inputs, one being the <2V high line from the line voltage detector (3) and the other from the busy tone detector (9). The delay timer (10) is set to send out a problem signal high only if the incoming signal is present for longer than a predetermined period. The timing of the delay timer circuit (10) is set to exceed the time elapsed before any subscriber normally would replace the telephone handset when he can not get through to a called number, for example 15 sec from the time the busy tone was first received.

If the subscriber chooses not to replace the handset until a time exceeding a timing set in the delay timer (10), the circuit treats it as if the telephone is in an "off-hook" condition and generates a problem signal which, in turn, activates the appropriate alarm for corrective action. The output of the delay timer (10) passes through to an alarm circuit (12) and lo a fault indicator (13). This timer circuit (10) also has a power-up reset circuit to prevent sending out a problem signal high to the alarm during the power-up process.

A line status detector (11) has two inputs, the output of the line voltage detector (3) on the <2V high line and the output of the busy tone detector (9). It detects the immediate changes in the "busy tone present" in the signals present on these lines. It produces a high (fault) signal only for as long as one of the incoming signals is high. As soon as they are both low, it sends out a low (clear) signal preventing the alarm from activating, even though the delay timer (10) has counted down beyond the predetermined timing. This low signal prevents the alarm activating even though a trigger (problem) signal is received by the alarm circuit (12) from the delay timer (10) circuit.

The alarm circuit (12) receives the problem signal from the delay timer (10) and a fault signal from the line status detector (11 ). As long as the problem signal is high and the fault signal is high, the alarm circuit (12) will provide an alarm through a beeper (15). Once at least the fault signal is low, it stops.

The line status detector (11) reacts instantly to the incoming signals. Thus it stops the alarm once the problem is rectified.

Whilst beeper (15) indicates if there is a problem, the faujt indicator circuit (13) indicates to the telephone subscriber what type it is. It has inputs from the output of the delay timer (10), the busy tone detector (9), and the <2V line from the line voltage detector (3). It indicates which of the two following possible faulty conditions has occurred:

1. the telephone apparatus or the telephone is open or short circuited, or

2. the telephone receiver is in "off-hook" or busy.

It does this through different LEDs, LED1 for open/shorted line and LED2 for off-hook. Additionally a mute button (16) is connected into the alarm circuit (12). This is usable by the telephone subscriber to disable or inhibit the alarm in the event that the subscriber deliberately places the handset in the "off-hook" position and does not want to be disturbed by the alarm.

The battery (14) powers the various circuits (6) - (10) and (12) in the event that the incoming voltage is below 30 V. It also powers the line voltage detector (3) whatever the incoming voltage.

There is, however, an ON/OFF switch (1.7) between the battery and the DC power switch (4) and between the battery (14) and the line voltage detector (3). This is also manually operable by the user. Turning OFF this switch prevents the alarm from sounding, for instance when the apparatus is not plugged into the telephone line, at which point no voltage would be detected. This is the same condition as the telephone line being open or short-circuited.

Further description will now be made of the operation of the apparatus of Figure 1 under certain conditions:

1. At least one of the telephones connected in parallel is in a "off-hook" condition:

If any of \the telephones is in a "off-hook" condition, then the voltage level in the incoming signal drops and the line voltage detector detects it to drop below 30V. A <30V high signal is sent out to the DC supply switch (4). Thus power is supplied to the rest of the circuitry from the battery (14). After a while, as shown in figures 2 and 3, a busy tone is generated at the exchange (assuming no number has been called or the called number is busy). This passes from the bridge polarity guard (1) through the AC coupler (5), the busy tone frequency filter (6), the audio amplifier (7) and the waveform converter (8). The signal leaving the waveform converter, in the case of a signal as in Figure 2, is in the form of alternating 0.75 sec HI and 0.75 sec LO pulses. The busy tone detector (9) detects a busy tone and sends out a "true" logic signal to the delay timer (10). Once this "true" signal has gone on longer than the predetermined timing, the alarm circuit (12) alerts the subscriber by the beeper (15). At the same time the coincidence of the problem signal from the delay timer (10) and of the true signal from the busy tone detector (9) in the fault indicator (13), causes LED 2 to light up, thereby indicating that an "off-hook" condition has occurred. The subscriber then can rectify the fault.

The alarm circuit (12) will be released when the line status detector (11) detects a "clear" signal, which can only happen when the subscriber replaces the handset and the telephone line is not open or short circuited.

2. At least one of the telephones connected in parallel has become open or short circuited or the incoming line itself is open or short circuited (i.e., it goes "dead"):

If any of the telephones has become open or short circuited or the incoming line itself is open or short circuited, then the voltage level in the incoming signal drops and the line voltage detector (3) detects it to drop below 2V. A <2v high signal is sent out to the delay timer (10) and fault indicator (13). As the voltage is also below 30V, a <30V signal is also set to the DC supply switch (4) to power the circuitry. After a time, the output from the delay timer (10) goes to high to cause the alarm circuit (12) to alert the subscriber by the beeper (15) and fault indicator 13 causes the LED 1 to light up, thereby indicating an open or short- circuit in one of the or the incoming line has occurred. The subscriber then can rectify the fault, by removing the offending telephone or alerting the telephone company (using another iine).

Again the line status detector (11) detects a "clear" signal and sends out a fault low signal once the problem is rectified.

Variations to the embodiment of the figure 1 are possible. Some variations of such examples are set below.

The ON/OFF switch (17) need not be manually operable or only manually operable. It could operate automatically (mechanically), for instance to be closed (i.e. ON) whenever the apparatus is plugged in, and to open (i.e. OFF) when it is unplugged. The <30V output and DC supply switch (4) may be dispensed with so that power is always supplied to the various circuitry. However, they are useful because they prevent power from draining to the various circuits when the telephone is on the hook.

The 2V and the 30V levels and other specified properties are not necessarily essential. Other levels may be set according to what may be deemed "dead", "off-hook" etc.,

Different telephone equipment manufacturers may have their own way of generating and using the various service tone signals, which may be customised according to the requirement of the telecommunication authority of each country. Figures 2 and 3 show, by way of example, signaling in Singapore and the Republic of China (Taiwan). Thus, the telephone service tone signals may vary from country to country and installation to installation. Voltages and timings may also vary.

Instead of the Bridge Polarity Guard (1) there may be an AC to DC adapter to derive the necessary DC voltage to the line voltage detector (3) and the battery charging circuit (12). Instead of the bridge polarity guard (1), battery charging circuit (12) and the rechargeable battery (14), there may be a DC battery to provide the necessary DC voltage to the line voltage detector (3) and other circuitry. Another possibility is to provide the power from the mains. This is preferably with some form of battery (rechargeable or otherwise) in case of power failures.

As described the waveform converter (8) converts its incoming signal only according to the length of specified frequency signals. It can also use the amplitude of those signals as a trigger to provide the pulses. Of course other possibilities for detecting "off-hook" signals can equally be used.

The beeper (15) is only used with one tone in the above embodiment, to send an alarm. By modifying the input to the alarm circuit (12), it is possible to control the beeper to emit different signals according to the type of problem. Other possibilities include replacing the <2V high signal and busy tone true signal inputs to the fault indicator (13), with the output from the line status detector (11).

Figure 4 is a preferred embodiment of an apparatus for detecting line busy condition in a telephone receiver in a system having several receivers in parallel on the same line.

As indicated the line has two receivers A and B connected in parallel. A bridge polarity guard (1) which is a full wave rectifier circuit is also connected across the line. This provides power to a voltage detector (3). In this regard it is similar to what is shown in Figure 1.

A line busy detection circuit 18 is connected to the voltage detector. This circuit comprises a transistor whose base is connected to the output of the voltage detector (3) through a resistor R1. The emitter of the transistor is connected to a resistor R2 whose other end is connected to ground. The collector of the transistor has an LED in series. The anode of the LED is connected the bridge polarity guard (1).

When one of the receivers A or B is picked up, the voltage detector (3) detects the presence of a < 30V signal indicating a "off-hook" condition, as in Figure 1 , voltage detector (3) produces a logical high signal. In this condition the transistor T1 switches on thereby switching on the LED. When the LED switches on, a potential user can see that the line is busy. He can then wait until the LED is off or, if it is on for too long, he can investigate and take corrective, if necessary.

Once the telephone receivers A and B are back on the hook, the voltage to the voltage detector (3) goes back up and the signal output from the voltage detector (3), goes low, whereby the transistor T1 is switched off, thus switching off the LED.

The output of the bridge polarity guard (1) acts as a DC power supply to the LED.

This circuit can be incorporated into a telephone receiver, or plugged into one, or plugged into a telephone socket. Figure 5 combines the circuit of Figure 1 with the line busy detection circuit (18) of Figure 4.

Thus it can detect faults, engaged tones and when the line is busy.

As shown in Figure 5 the power supply to the anode of the LED is derived from the DC power supply switch (4) following a detection of a low voltage by the voltage detector (3). However, as shown in dotted lines, the power supply can alternatively be derived from the battery (14) or the bridge polarity guard (1).

Other variations discussed earlier may also apply to this circuit.

The LED can be modified to add more visual effects. For example it can be a blinking LED, or there can be two LEDs, one for free line and the other for busy line.

The above description is merely exemplary. Other modifications and variations fail within the scope of the invention, including as defined in the appended claims.

Claims

1. Apparatus for connection to a telephone line, comprising: detecting means for detecting the presence of a low voltage on said telephone line; and alarm means to be activated by an alarm activation signal from said detecting means in response to detection of a low voltage by said detection means.

2. Apparatus for connection to a telephone line, comprising :

. detecting means, for detecting an open or short-circuit on said telephone line; and alarm means to be activated by an alarm activation signal from said detecting means when an open or short-circuit is detected by said detection means.

3. Apparatus according to claim 1 or 2, wherein said detecting means is operable to detect a voltage on said line.

4. Apparatus according to claim 1, 2 or 3, wherein said detecting means is operable to detect a low voltage corresponding to an open or short circuit.

5. i Apparatus according to claim 1 or 4, operable when said low voltage on said line is μe to a fault on the line or to a fault in equipment connected to the line.

6. Apparatus according to any one of claims 1 and 3 to 5, wherein said detecting means further comprises switch means operable to supply power to said alarm means when the voltage drops below a first predetermined value.

7. Apparatus according to claim 6, wherein the first predetermined voltage is a voltage corresponding to a voltage when a telephone on said line is no longer on the hook.

8. Apparatus according to any one of claims 1 and 3 to 7, wherein said detecting means is operable to activate said alarm means when the detected voltage drops below a second predetermined value.

9. Apparatus according to claim 8, wherein said second predetermined voltage is a voltage corresponding to a voltage when there is an open or short circuit on the line.

10. Apparatus according to any one of preceding claims, wherein said alarm means comprises audio and/or visual indicator alert means.

11. Apparatus according to any one of preceding claims, wherein said detecting means comprises a first detector means for detecting the voltage on said telephone line.

12. Apparatus according to claim 11, wherein said first detector means comprises a voltage divider network.

13. Apparatus according to any one of preceding claims operable to be powered by a rechargeable battery.

14. ^ Apparatus according to claim 13, further comprising a battery charging circuit to charge said rechargeable battery.

15. Apparatus according to claim 14, wherein the charger circuit is powered from the telephone line.

16. Apparatus according to any one of preceding claims, further comprising a full wave bridge rectifier circuit, operating independently of the telephone line polarity.

17. Apparatus according to any one of the preceding claims, wherein said detecting means comprises a second detector means to detect an "off-hook" condition of a telephone on said telephone line.

18. Apparatus according to claim 17, wherein said second detector means comprises a busy tone detection means for comparing properties of an incoming signal with predetermined values to determine if the incoming signal is or contains a busy tone signal, for sending an activation signal to the alarm means.

19. Apparatus according to claim 18, wherein said busy tone detection means comprises a waveform converter for converting an analogue busy tone signal into a digital pulse signal.

20. Apparatus according to claim 19, operable on the basis that said busy tone signal includes signal bursts of a predetermined duration and said digital pulse signal is of the same duration.

21. Apparatus according to any one of the preceding claims, wherein said alarm means comprises delay timer means for preventing activation of said alarm means, unless and until the alarm activation signal lasts at least a predetermined length of time.

22. Apparatus according to any one of the preceding claims, further comprising rriuting means for inhibiting the alarm means.

Zά. Apparatus according to any one of preceding claims, further comprising second switch means to prevent operation when the apparatus is not connected to said telephone line.

24. Apparatus according to any one of the preceding claims, further comprising a plugging means for plugging into a telephone socket.

25. Apparatus according to claims 23 or 24, wherein said second switch means automatically switches said apparatus ON when said apparatus is plugged into a socket and OFF when said apparatus is unplugged from said socket.

26. A method of detecting in-operable conditions on a telephone line, comprising: detecting the presence of a low voltage on said telephone line; providing an alarm activation signal when said low voltage is detected; and activating an alert in response to an alarm activation signal.

27. A method of detecting in-operable conditions on a telephone line, comprising: detecting the presence of an open or short-circuit on said telephone line; providing an alarm activation signal when said open or short-circuit is received; and activating an alert in response to said alarm activation signal.

28. A method according to claim 26 or 27, wherein said detecting step comprises detecting a voltage on said line.

29. A method according to claim 26, 27 or 28, wherein said detecting step comprises detecting a low voltage corresponding to an open or short circuit.

30. A method according to any one of claims 26, 28 and 29, wherein said detecting step further comprises the step of supplying power to allow said alert to be activated when the detected voltage drops below a first predetermined value.

\

31. \ A method according to any one of claims 26 and 28 to 30, wherein said detecting step further comprises the step of providing said alarm activation signal when the detected voltage drops below a second predetermined value.

32. A method according to any one of claims 26 to 31 , further comprising the step of charging a rechargeable battery.

33. A method according to claim 32, wherein said recharging step derives power from the telephone line.

34. A method according to any one of claims 26-33, further comprising a second detecting step of detecting an "off-hook" condition of said telephone line.

35. A method according to claim 34, wherein said second detecting step further comprises: comparing properties of an incoming signal with predetermined values; determining thereby if the incoming signal is a busy tone signal; and activating the alert if a busy tone signal is so detected.

36. A method according to any one of claims 26 to 35, wherein said alert activation step includes the step of preventing the activation of the alert unless and until the alarm activation signal lasts at least a predetermined length of time.

Apparatus for connection to a telephone line, comprising: detecting means for detecting a line busy signal on said telephone line; and indicator means to be activated by the detection means in response to detection of a line busy signal by said detection means.

38. Apparatus according to claim 37, wherein said line busy signal results from detectipn of a reduced voltage on a line.

39. Apparatus according to claim 37 or 38, further comprising a bridge rectifier to supply DC supply voltage to said indicator.

40. Apparatus according to any one of the preceding claims, wherein said indicator means is an LED.

41. Apparatus according to any one of claims 37 to 40 wherein said indicator means is located within the telephone receiver unit.

42. Apparatus according to any one of claims 1 to 25, in combination with the apparatus of any one of claims 37 to 41.

43. A method of indicating if a telephone line is busy, comprising: detecting a line busy signal on said telephone line; providing an activation signal when the line busy signal is detected; and using said activation signal to activate an indicator that the line is busy.

44. A method according to any one of claims 26 to 36, in combination with tha method of claim 43.