GB2093242A - Sound system and a warning device therefor - Google Patents

Abstract

A warning device 3 is provided to override the signal from domestic sound equipment 1 to headphones 2, in the event that a sensor 5 or 6 responds to the sound of a telephone or door-bell. <IMAGE>

Description

SPECIFICATION Domestic sound system and a warning device therefor Modern domestic sound equipment is adapted to allow the listener to use headphones as an alternative to loudspeakers. A prob problem that arises when headphones are being used is that it is impossible for the listener to hear other sounds, such as the ringing of a door-bell or telephone. It has already been proposed to overcome this problem by adapting the headphones so as to admit extraneous sounds. This solution, however, has the disadvantage that the listener may then be distracted by extraneous sounds which he deliberately wishes to exclude. The problem also arises to some extent, especially for the hard of hearing, when loudspeakers are in use and the volume is high.

These problems are overcome by the sound system and warning device to be described hereinafter by way of example with reference to the drawings, in which: Figure 1 illustrates diagrammatically the sound system in combination with a warning device, Figure 2 shows the circuit of the warning device, Figure 3 shows a modification to the circuit of Figure 2, and Figure 4 shows the circuit modified to switch in video equipment.

Referring to Figure 1, an existing item of sound equipment used in the home is shown at 1. This equipment may include a television or radio receiver, as well as a disc and cassette player. The output from the equipment may be supplied to loudspeakers, not illustrated, or to headphones 2 having a plug normally inserted into a socket in the equipment. As proposed herein, the equipment is supplemented by a warning device 3 including an input lead 4 with a plug which is inserted into the headphone socket of the sound equipment in place of that on the headphone lead.

The warning device further includes sockets for receiving plugs on the headphones, and lines from microphones or other sensors 5, 6 responsive to sound generated by the telephone and the doorbell or door-knocker. Provided on the device are lamps to indicate the input of signals from either sensor, as well as a reset button. Naturally, the device also includes terminals for connection to the domestic power system for operating an internal power supply, and an on/off switch.

Although as illustrated, the warning device is shown as a unit separate from the sound equipment, it may be incorporated within the latter.

Within the warning device is a circuit adapted upon the input to the device of a signal from either sensor 5 or 6 to override the signal from the. sound equipment and supply to the headphones a signal indicative of operation of either or both of the sensors 5 and 6, as the case may be. As will shortly be described in detail, the preferred circuit operates to interrupt the signal from the sound -equipment and to substitute therefor the actual sound generated by the telephone or door-bell. At the same time, the indicator lamps on the device become lighted. This condition of the device continues until operation of the reset button.

Of course, modifications may be made to this preferred arrangement. Thus, for example, the input signals from the sensors may result in the warning device generating a distinct signal instead of transmitting signals from the sensors. Such an arrangement may be particularly advantageous it the case of the operation of the door-bell sensor, the signal from which may be of short duration.

Instead of terminating the signal from the sound equipment aitogether, the level of this signal may be reduced and have that generated or transmitted by the control device to reset automatically. Finally, although the system is essentialiy intended for use in conjunction with headphones, in certain circumstances it may be convenient for it to be used in conjunction with loudspeakers. These and other modifications are intended to fall within the scope of the inventive concept as will appear from the appended claims.

Referring now to Figure 2, the circuit of a preferred warning device and associated equipment will now be briefly described.

Microphones 5, 6 are as described above used to sense the operation of the telephone and doorbell. The microphone employed may be a contact microphone attached to the apparatus in question so as to pick up only the vibration or sound of that apparatus, and not the surrounding sounds.

The input lines of the headphones, again indicated at 2, are connected to ganged movable contacts Ra 1 and Ra2 of a relay Ra. These contacts normally occupy the illustrated position engaged with fixed contacts connected to lines leading from the sound equipment. Upon operation of the warning device, the relay switches over to break the circuit from the sound equipment and to make a circuit through the warning device whereby the headphones receive a signal arising as a result of operation of either of the sensors 5 and 6.

The relay Ra is included in a circuit through a transistor T1 coupled to the power supply of the warning device. Transistor Ti is normally nonconducting so that the relay is de-energised and its contacts occupy the illustrated position, but may be rendered conducting by an arrangement of NOR gates G1 and G2. Gate G1 has a first input controlled by a second transistor T2 connected to an arrangement of resistors Ti, R2, R3 and R4 and, by way of capacitor C2, to a mixer 7 receiving signals from sensors 5 and 6. A second input of gate G 1 is connected to a feedback loop from the output of gate G 1.The gate G2 has three inputs, namely a first input connected to the output of gate G 1, a second input connected to a rest circuit including a pushbutton contact 10 and a third input connected to a circuit including capacitor C3 and resistor R5. In the absence of signals from sensors 5 and 6, there are low signals at both inputs of gate G 1, and a high signal at its output.

Consequently, there is a low signal at the output of gate G2, since the connection through resistor R6 to the negative terminal ensures that there is a low signal on the second input until such time as the push-button contact 10 is closed. The third input to gate G2 provides a high going pulse at switch on, ensuring the memory gates G 1 and G2 do not latch on.

The door-bell and telephone indicator lamps 8 and 9 are constituted by a pair of LED's the operation of each of which is controlled by a respective arrangement of NOR gates G3 and G4, and G5 and G6, respectively, each gate arrangement being similar to that consisting of gates G 1, and G2, with the exception that each of gates G4, G6 has but two inputs, one connected to the output of the assciated gate G3 or G5, and other to terminal X of the reset circuit.

Operation of the circuit takes place as follows: in the absence of any signal from sensors 5 and 6, transistorT2 is switched on via resistors R1 and R2 by a suitable selection of the values of resistors R1, R2, R3 and R4. The collector voltage of transistor T2 is held at a value too low to switch on NOR gate G 1.

Upon actuation of one of the sensors, an AC signal is transmitted from mixer 7 via capacitor C2. Transistor T2 stops conducting at a rate determined by the AC frequency. With transistor T2 rendered momentarily non-conductive, its collector voltage rises almost to HT potential, and gate G 1 is switched on, producing a low signal at its output. With low signals at all its inputs, gate G2 now has a high output which switches on transistor T1 to operate relay Ra. The feed-back signal to the second input of gate G 1 latches gates G 1 and G2 in their on condition, so that the relay remains energised. The relay contacts switch over so that the output from the sound equipment is terminated and the signal which is fed to the headphones depends upon the output from the mixer.The operation of the relay is instantaneous, so that a signal from the sensors of even extremely short duration is sufficient to cut off the existing sound source, the signal being heard in full. One gate arrangement G3 and G4 or G5 and G6 operates in a similar fashion to the gate arrangement G 1 and G2 so that one of the LED's 8 or 9 becomes illuminated. The activated condition of the circuit is held until the reset contact 10 is closed to supply a high signal to one input of the second gate in each arrangement, thereby restoring the low signal at the output of the second gate, and unlatching the previously latched gate arrangements. It will be noted from the circuit that the operation of one sensor followed by the operation of the other will result in both signals being heard through the headphones and both lamps lighting.

Referring now to Figure 3, where is shown the circuit of Figure 2 modified to include time sensitive circuitry.

Operation is as follows: A ringing current from the telephone sensor is rectified by diode D1 and stored by capacitor C5. When capacitor C5 is fully charged, relay Rb is operated through the swtiching of T3. Rb is self latching through Rb2 to prevent the draining away of current through R1 1 (e.g. between rings) causing the relay Rb to re-open. Operation of the switch Rbl allows the signal from the telephone sensor to enter a mixer 7. Variable resistor VR 12 is used to vary the length of time taken for ringing current to operate relay Rb. R10 is a current limiting resistor and Ru (as previously described) is used to discharge the capacitor. Operation of the reset button (1 0a) also operates 1 Ob consequently unlatching relay Rb.

the time-sensitive circuitry therefore ensures that only a continuous ringing tone can operate the device. Consequently, the device is not actuated by occasional rings as may for example be caused by knocking the receiver or through faults on the line.

Referring now to Figure 4, the circuit therein shown allows the sound of a door-bell, telephone or other equipment to be monitored, to be heard through the loudspeaker/earphone socket of a domestic television receiver, the connection being made through the aerial socket thereof. By making use of a video camera, VC, suitably positioned to scan the doorstep or a card bearing wording, a picture of the caller or the legend 'doorbell' ringing may appear on the screen. Instead of making use of a door-bell monitor, a pressure sensitive or other device responsive to the presence of a caller may be used to operate the system.

The proposed system is especially useful for the partially deaf who tend to use audio equipment with the sound turned full up such as to drown out the sounds from the door-bell or telephone.

Although the systems described above are primarily intended to provide an indication of the ringing of a door-bell or telephone, they may be modified to indicated other domestic events, such as the activation of a fire or other alarm, a calling device from a sick room or a baby alarm, for example. Similarly, aithough the main use of the systems will be in connection with equipment of the so-called music centre type, they may be used to provide a warning signal overriding the normal output of any domestic sound equipment.

Claims (5)

1. A domestic sound system including equipment for supplying an electrical signal in response to operation fo radio, disc, cassette or other means, and apparatus for converting said electrical signal into sound waves, in combination with a warning device adapted to provide said apparatus with a warning signal in response to operation of a sensor located or arranged to detect the happening of a preselected event.

2. A system as claimed in claim 1, wherein said apparatus comprises headphones.

3. A system as claimed in claim 1 or 2, including sensors arranged to detect sound from a telephone and sound from a door-bell or doorknocker, respectively.

4. A warning device including a relay having a contact movable from a first position for transmitting electrical signals from sound equipment to headphones into a second position for transmitting an electrical warning signal to the headphones, and a control circuit for operating said relay in response to a signal from a sensor, or from one of a number of sensors, means for resetting the relay, and a circuit for causing the indicator lamp to light in response to a signal from the sensor, or from one of a number of sensors.

5. A domestic sound system substantially as hereinbefore described with reference to any figure of the drawings.