GB2362739A - Selectable public address system - Google Patents

Abstract

An audio system having a control unit (2) and several loudspeakers (4, 6 and 8) connected in parallel with each other, the loudspeakers each having a unique address and the control being arranged to broadcast a plurality of audio channels and to communicate to each loudspeaker by means of a unique address so as to instruct a particular loudspeaker of the loudspeakers connected to the control to receive a particular audio channel.

Description

2362739 Improvements in and relating to audio systems The present

invention relates to aud'LO systems and amplifiers and controls, loudspeakers, and the associated interconnections therefor.

Audio systems having many loudspeakers are known. Examples of such are fire alarm systems and other public address systems. They are used in many commercial and public buildings. In such buildings, it is often necessary to provide different audio signals to different areas or zones within a building. Known systems, require the zones to be planned before installation, and lack the flexibility to be re-configured on an ad hoe basis during a period of operation, for example, during a day, when the use of a building may change with the time of day, or as a result of other un-predictable occurrences. This is a particular information required to problem for audio systems intended to impart to the occupants of a building, when it is only impart that information to a selected zone or location within the building where an incident, such as a fire or other emergency, has occurred. With known systems, complex wiring topologies have to be adopted to try and accommodate future requirements at the time of the installation.

According to the present invention, there is provided an audio system comprising a control and at least two loudspeakers connected to the control, the loudspeakers 2 being connected in parallel with each other, the loudspeakers each having a unique address, the control having means to broadcast a plurality of audio channels, and the control being arranged to communicate to each loudspeaker by means of the unique address so as to instruct each loudspeaker to receive a particular audio channel.

A benefit of the invention is that an installer does not have to have knowledge of the zoning requirement when installing the speakers and the wiring between the speakers and the control.

A further benefit of the invention is that the audio system allows the transmission of several audio channels simultaneously into different zones within a building, so that in a multiple occupancy building the output from the loudspeakers may be tailored to the requirements of each occupier. Examples of such buildings would be airports or shopping complexes.

Preferably the audio system is arranged so that the at least two loudspeakers may emit different signals at the same time.

A benefit of the loudspeakers being able to emit different signals, is that this may be achieved without the necessity for separate amplifiers and connections that are required in a conventional public address or voice alarm system.

In an embodiment of the invention the loudspeakers are connected to the control by a two conductor system, that supplies both an audio data signal and electrical power to operate the loudspeaker.

A benefit of the first embodiment of the invention is that installation of the system is simpler and cheaper than known systems zoned by the structure of the wiring.

In a further embodiment of the invention, the loudspeakers are provided with a separate audio data signal and a separate power supply. In this embodiment there are preferably four conductors interconnecting a loudspeaker with the control.

A benefit of the second embodiment is that the power supply may be separated from the audio channels, and, in a large system, power may more easily be supplied to remote loudspeakers.

Preferably, in the further embodiment the loudspeaker is arranged to provide a fault signal should the loudspeaker fail to receive an audio data signal.

Preferably, the control is arranged to individually communicate the volume output level for each loudspeaker to that loudspeaker.

A benef it of this is that the control may be arranged to monitor the loudspeaker to detect correct or faulty operation.

Preferably, the control and the loudspeakers are arranged to enable the control to receive information from a particular one of the loudspeakers.

4 A benefit of this is that defective loudspeakers may be detected more easily than on a conventional system where the only measurable characteristic of a loudspeaker is that Of -the load placed on the cable by each of the speakers connected in parallel on the circuit. If a large number of speakers are connected to a single cable, the difference in load caused by one speaker being defective may be as little as 1% or less, which is difficult to measure.

Preferably, the audio information to the control for relaying to the loudspeakers may be controlled from at least two locations.

Preferably, a volume level of the output from each loudspeaker may be set independently from the others by a signal from the control.

A benefit of this is that in a conventional system with the speakers connected in parallel with each other, the volume on an individual speaker may only be set by altering a physical connection within the speaker housing itself. This is time consuming in areas such as atriums with high ceilings where access to the speakers is difficult.

Preferably, at least a loudspeaker is arranged to sense the level of ambient noise and to adjust the volume level of its output accordingly.

Preferably, at least a loudspeaker is arranged to allow a person within the range of the speaker to adjust the volume level of its output.

A benefit of this is that in an application such as a hospital, it may be inappropriate for the speaker to make a loud noise, such as in an operating theatre, or in a particular ward.

Preferably, the information on each of the audio channels is digitally encoded.

A benefit of this is that the quality of the audio information received by the loudspeaker is enhanced. This improves both the clarity of voice announcements and improves the quality of background music when compared with an analogue connection between the loudspeakers and the control.

Preferably the control of the audio system is arranged to be connected to one or more fire detection devices.

Preferably the audio system is be arranged to instruct at least a particular loudspeaker to receive and broadcast a particular audio channel when at least one fire detection device provides an alarm signal to the control.

A benefit of this is that a fire detection device, such as a smoke alarm or a fire alarm system, may provide an alarm signal to the control, so that the audio system may provide a specific audio broadcast from a particular loudspeaker. Such specific audio broadcast could include information to enable safe evacuation of people at risk from a fire.

Specific embodiments of the described by way of example accompanying drawings in which invention will now be with reference to the 6 Figure 1 is a diagram of an audio system according to a first embodiment the invention; Figure 2 is a diagram of an audio system according to a second embodiment of the invention; Figure 3 is a diagram of an audio system according to a third embodiment of the invention; Figure 4 is a block diagram of a suitable control for the audio system of either Figure 1, 2 or 3; and Figure for a 1, 2 or 3.

is a block diagram of a suitable speaker control loudspeaker for the audio system of either Figure From Figure 1, an audio system 1 may be seen to comprise a control or system unit 2 and loudspeakers 4, 6 and 8 which are connected in parallel with each other to wires 19 And 20. The loudspeakers 4, 6 and 8 and their interconnections form speaker system 26. When used as a part of an alarm system, wires 19 and 20 are preferably encased in a protective sheath 18, such as that of a mineral insulated copper clad (MICC) cable, or a fire resistant plastics or rubber sheath. The control or system unit has an input means 14 which may be a keypad, a feedback means 16 which may be an array of light emitting diodes or a visual display unit, an audio input means 10 which may be a microphone or telephone handset, an interface to an alarm sensor 11 or a fire detection system and an associated fire alarm control panel, and a music source 12 which may be radio, tape or digital disc equipment. The control or system unit 2 further 7 comprises processing means 24 to address each of the loudspeakers, and to process information for one or more audio channels for broadcasting to the speaker system 26. Each loudspeaker 4, 6 and 8 has a speaker control 34, 36 and 38 which forms an interface between the wires 19 and 20 and the sound genera-Ling element 44, 46 and 48 of each loudspeaker.

Figure 2 shows a block diagram of a second audio system 200 according to a second embodiment of the invention. The audio system 200 comprises both a fire alarm system and a speaker system 226 and would be suitable for use in a relatively small installation. The audio system 200 comprises a control or system unit 202 and groups of loudspeakers 204, 206 and 208, each group comprising one or more louds)eakers 250, 251, 252, 253, 254, 255, 256, 257 and 258. Within connected in parallel system units 260, 262 units 260, 262 and 264 the control 202, which across which each of loudsneakers 204 206 each group the loudspeakers are with each other to control or and 264. The controls or system are interconnected by loop 266 to comprises at least two conductors the controls or system units is connected in parallel with each other. The groups of and 208 and their interconnections. To the loop 266, fire detectors 275 and 276 and break glass call points 277 are also connected in Qarallel with form speaker system 226 2 7 0, 2 7 2, 2 7 3, 271, 274, and each other and in parallel with the loudspeakers to the control 202. which may be a The control 202 has an input means 214 keypad, a feedback means 216 which may be 8 an array of light emitting diodes or a visual display unit. The control 202 further comprises processing means 224 to address each of the loudspeakers, and to process information for one or more audio channels for broadcasting to the speaker system 226. The control 202 may also comprise a battery backup power supply 203. The controls or system units 260, 262 and 264 each form an interface between the wires 219 and 220 and the loudspeakers in their respective groups of loudspeakers. Each of the controls or system units is provided with a separate power supply 261, 263 and 265 respectively.

A benefit of having a separate power supply to each control or system unit is that a distance between the controls may be extended without suffering from a voltage drop along a power supply cable. A benefit of having a loop 266 is that the reliability of the system is improved, since there are two connection paths between each device on the loop and the control.

Figure 3 shows a diagram of a third audio system audio system 300 according to a second embodiment of the invention. The audio system 300 comprises both a fire alarm system 320 and a speaker system 326 and would be suitable for use in a relatively large installation, and for example the system is arranged such as might be in a three floor multiple The audio system 300 302 and 303, system units and 335 and groups of 308. Group 304 comprises required in an installation occupancy office building. comprises three controls 301 330, 331, 332, 333, 334 loudspeakers 304, 306 and 9 loudspeakers 350, 351, 352 and 353 connected in parallel with each other on speaker loop 354 to system unit 331, and the other groups are similar.The system units 330, 331, 332, 333, 334 and 335 are interconnected by loop 366. The loop 366 comprises at least two conductors is parallel with each other. The groups of loudspeakers 304, 306 and 308 and their interconnections form speaker system 326.

across which each of the svstem units connected in The fire alarm system 320 is formed of three sub-systems 322, 324 and 326, each of which has control 301, 302 and 303 respectively. Fire alarm sub-system 302 has tWO detector loops 328 and 329. Detector loop 328 having call point 342 and fire detectors 343, 344 and 345, and detector loop 329 having fire detectors 346, 348 and 349 and call point 347, all call points and fire detectors being preferably connected in parallel with each other on an at least two conductor system. The other sub-systems 326 and 328 are similar to sub-system 322. Interconnections between the speaker system 326 and the fire alarm system 320 through the system units enable signals from input means 310, 311 and 312 which may be keypads, remote input 313 which may be through a telephone line connection, and signals from microphones 314, 315 and 316 to the controls 301, 302 and 303. The input means may also have feedback means which may be an array of light emitting diodes or a visual display unit which is arranged to receive information from the controls. Each of the controls 301, 302 and 303 further comprises processing means 317, 318 and 319 to address each of the loudspeakers, and to process information for one or more audio speaker system 326.

is channels for broadcasting to the The controls may also comprise a battery backup power supply and electrical power may be supplied to one control or system unit and then distributed to the other controls and system units, bUt more. preferably the electrical)ower supply 370, 371, 372, 373, 374 and 375 is connected at each of the system units. Still more preferably, the electrical power supply is also connected to each of the controls. The system units 331, 333 and 335 each form an interface between the loop 366 and the loudspeakers in their respective groups of loudspeakers. Each of the system units 330, 332 and 334 may be provided with Hence have their floor, which may include control over background music and public address announcements, adjusting the volume levels of individual loudspeakers, and setting fire detector parameters to suit the current occupancy of the building. Overall control of the whole system may be arranged to be provided from any local or remote input means.

a background music input device 376, 377 and 378. each floor of an office building may be enabled to full or limited control over the audio system on

Preferably, each of the system units of Figures 2 and 3 also comprise an audio digital multiplexor.

Figure 4 shows a block diagram of a suitable control or system unit for the audio system of either Figure 1, 2 or 3. The control or system unit or audio digital multiplexor has preferably up to eight audio inputs or channels, four through the local A/D interfaces and four from other controls through the ADM loop.

The un-encoded audio from the local A/D's is passed to the DSP where it is encoded into MPEG audio. These 4 channels from the ADM loop and any required locally stored messages. The cross-switch then selects the four channels required for the locally connected speakers and transmits them over the speaker loop with any control information required multiplexed in from the processor.

Channel selection information is written into registers in the crossswitch device by an on-board microcontroller DSP fitted for this purpose.

Non-volatile memory E2 is provided to retain information required for the operation of the micro-controller DSP.

The cable driver combines the transmitted data with power fed into it from the local power supply unit PSU. A period clear of data is allowed every frame to allow the speakers to transmit back to the control or system unit ADM.

One or more of the system units of Figures 2 and or 3, may also comprise a personal computer, or similar, provided with a display arranged to provide information about, and input means to interact with, the whole audio system.

Preferably, the audio systems of Figures 2 and 3 are arranged so that each control and / or system units having an audio digital multiplexor has several input / 12 output connections. Each such audio digital multiplexor ADM. preferably has four, time division multiplexed (TDM) digital audio channels and control data, both to and from each audio digital multiplexor ADM, and power supplied by the ADM through a single two wire or 'Lour wire cable to a number of information instructing transmit or speakers. The speakers receive control from the audio digital multiplexor ADM them which of the four audio channels to play. The control information also provides information to the speaker about parameters such as transmission or play volume, delay, and frequency response. The system units or audio digital multiplexors are interconnected by means of the ADM loop interface o Figure 4.

Preferably the system units are arranged so as to be interconnected as a peer to peer network.

A multiplexor Mux may be provided to multiplex control data from the micro-processor and audio data from the cross-switch.

A speaker loop control interface SP connect loudspeakers to the system unit is provided to The speaker loop control interface may provide both a data signal and electrical power to the loudspeakers. The electrical power is provided by means of a mains power supply unit PSU and an associated Speaker PSU and a back-up battery charger and a low voltage PSU..

Preferably, the speaker can also answer request from the ADM such as providing information about its status and the ambient noise level near the speaker.

13 From Figure 5, a block diagram of a speaker control 534 similar to speaker control 34 of loudspeaker 4 is shown. Such a speaker control would also form part of the loudspeakers of Figures 2 and 3. The control has an audio data input 402 and a separate power supply output 404.

Isolation devices 403 and 405, are preferably relays arranged to enable a damaged section of cable interconnecting two adjacent speakers to be isolated from the loop. Isolation of a damaged section of cable from the loop, breaks the loop into two sections each of which is still connected to a system unit at one end.

In the event of a the audio system being switched on, or after a short circuit has been detected, all the relays are returned to an open state. The control or system unit of Figure 4, is arranged to sequentially operate each relay to a closed "on" state, starting with the relays in each of the speakers nearest to the system unit. When operation of a relay results in the short circuit condition, the occurrence of a resystem unit repeats the sequential operation, stopping before the operation of the last closed relay. Hence operation of loudspeakers may be maintained even if a short circuit fault develops on a section of the speaker loop cable.

For use in the embodiment shown in Figure 1, the audio data input and the power input are connected together. The sound generating element comprises a speaker coil 406 and a diaphragm 408. A microphone 410 may be provided to enable the speaker control to monitor the ambient noise level. The microphone 410 is sampled through an analogue 14 to digital converter circuit 412 by a digital sound processor DSP, which may be arranged to locally direct the microph)ne signal to the local loudspeaker or may send the data back to the audio digital multiplexor ADM for further processing.

The speaker receives power and data from the control or system unit ADM. The dc power and data are separated by interface 418 and the dc power is converted to a low voltage to supply the circuitry on the speaker and to a higher voltage that is used to drive the speaker itself.

The data is decoded from the line and sent to the DSP. The DSP then acquires synchronisation with the data frame structure. A dialog takes place between the ADM and the speaker resulting in the speaker being allocated a unique number on the loop it is attached to. Control packets are used to change parameters on the speaker and it is assigned to one of the channels of audio being transmitted.

The assignment of the speaker to an audio channel may be changed by a subsequent control packet, so that the loudspeaker may receive a different channel as required.

The DSP takes the MPEG encoded audio data from the channel assigned to it and decodes it into normal 16 bit audio data samples. These samples are then sent to the D/A which converts them into an analogue waveform. This waveform is used by the speaker driver to drive the speaker and produce audio.

The delay memory is used as a simple delay line, if for acoustic reasons a time difference is required between the speaker receiving the audio and it being played.

A benefit of the delay memory is -that undesirable reverberation or echo effects perceived by a listener hearing several loudspeakers at once may be reduced.

A further benefit of the delay memory analogue waveform may be continuous, even i slight delay or interruption in the digital of information to the loudspeaker.

is that f there transmission Memory FLASH program, for processor DSP.

is provided to retain information such as a the digital signal processor or micro- An infra-red device IR is arranged to receive information from a remote infra-red device, so as to enable remote control of loudspeaker settings, such as the broadcasting volume.

16

Claims (11)

1. An audio system comprising a control and at least two loudspeakers connected to the control, the loudspeakers being connected in parallel with each other, the loudspeakers each having a unique address, the control having means to broadcast a plurality of audio channels, and the control being arranged to communicate to each loudspeaker by means of the unique address so as to instruct each loudspeaker to receive a particular audio channel.

   tem as claimed in claim 1, wherein the
2. 2. An audio sys,loudspeakers are connected to the control by a two conductor system.
3. 3. An audio system as claimed in claim 1, wherein the loudspeakers are provided with a separate audio data signal and a separate power supply.
4. 4. An audio system as claimed in any of the preceding claims, wherein the control is arranged to individually communicate the volume output level for each loudspeaker to that loudspeaker.
5. 5. An audio system as claimed in any of the preceding claims, wherein the control and the loudspeakers are arranged to enable the control to receive information from a particular one of the loudspeakers.
6. 6. An audio system as claimed in any of the preceding claims, wherein the audio system further comprises one or more fire detection devices connected to the control.
7. 7. An audio system as claimed in any of the preceding claims, wherein the audio information to the control for 17 relaying to the loudspeakers may be controlled from at least two locations.
8. 8. An audio system as claimed in any of the preceding claims, wherein at least a loudspeaker is arranged to sense the level of ambient noise and to adjust the volume level of its output accordingly.
9. 9. An audio system as claimed in any of the preceding claims, wherein at least a loudspeaker is arranged to allow a person within the range of the speaker to adjust the volume level of its output.
10. 10. An audio system as claimed in any of the preceding claims, wherein the information on each of the audio channels is digitally encoded.
11. 11. An audio system, substantially as hereinbefore described and with reference to the accompanying drawings.