Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B3/00—Audible signalling systems; Audible personal calling systems
  • G08B3/10—Audible signalling systems; Audible personal calling systems using electric transmission; using electromagnetic transmission
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B27/00—Alarm systems in which the alarm condition is signalled from a central station to a plurality of substations

Definitions

• the present invention relates to an electronic warning system, especially to such a system that emits an alarm (warning sound) of variable intensity and frequency.
• Warning devices are required in many industrial situations in order to give warning to personnel that machinery is about to start. Such devices have ge ⁇ erally been of the vibrating diaphragm or siren type, having a fixed acoustic output, operated automatically from a contact at the main switch panel of machinery. In order to allow time for personnel to move clear, the start-up of the machinery is delayed for a given period after the alarm has been sounded.
• an electronic warning system comprises a signal generator, a power amplifier and at least one loudspeaker.
• the system according to the present invention overcomes the limitations of the conventional warning devices by enabling. the alarm operating level, its acoustic frequency, its modulation pattern and its direction to be varied, thus providing the facility to optimise the audible impact on the personnel on the site whilst minimising the impact at the site boundary.
• the present system is suitable for both single and multiple signal source applications and is particularly suitable for applications - such as long conveyor belts, production lines, railways and hospitals - requiring multiple alarms from one contactor.
• the overall output is determined by the setting of the volume control of the power amplifier, it is desirable to provide means whereby the output level from the or each loudspeaker can be pre-set.
• an amplitude and frequency modulating device may be provided in order to provide the required pattern (e.g. a characteristic wailing, hi-lo or pulsed sound, etc.).
• each loudspeaker With the present system, central control of the or each loudspeaker can be achieved. Thus, it is preferred to pass the signal. from the amplifier through a multiplex coding unit, each loudspeaker being provided with a specific multiplex decoding unit.
• a multiplex coding unit each loudspeaker being provided with a specific multiplex decoding unit.
• the single accompanying figure represents a block diagram of a warning system in accordance with the present invention. Description of preferred embodiments
• a preferred embodiment of the present invention comprises a variable-frequency signal generator and a power amplifier providing a suitable output signal to one or more remotely sited loudspeakers.
• the alarm signal is produced in the signal generator and is then modulated by a programme selector in order to provide the means for optimising froth frequency and modulation for any background noise level.
• the acoustic output of the system is adjustable in three distinctly separate ways in order to achieve an optimum operating level and noise/warning contrast.
• the overall acoustic output of the system is adjusted via the main amplifier gain (volume) control.
• each individual loudspeaker is separately adjustable, by means of a secondary volume control, up to the maximum level set by the main amplifier level control. In practice, this is checked with a sound-level meter midway between two units to ensure that an adequate noise-to-background level is obtained. A value of 30 dB has proved satisfactory.
• the output of each individual loudspeaker could be electronically controlled to any desired level above the ambient noise level, by using the loudspeaker itself or an associated transducer as a feedback device.
• a programmable timer is incorporated in order to provide the facility of varying the overall level to produce an optimum setting both for day and for night operation.
• This last feature is particularly important as background levels often drop by 10 dB or more at night, during which period any high industrial boundary noise levels are most likely to give rise to complaint (see British Standard (BS) 4142 - Method of Rating Industrial Noise. Affecting Mixed Residential and Industrial Areas).
• the system of the present invention can be used in applications where only one loudspeaker is required.
• the present system is particularly advantageous in applications requiring two or more warning devices associated with a particular item of plant, it being necessary only to extend the number of remotely sited loudspeaker units.
• the individual speakers can be operated either simultaneously or in a desired sequence
• a multiplex coding unit and multiplex decoding units are provided, whereby sequential operation of the loudspeakers can be achieved.
• the multiplexing technique allows individual adjustment of volume for each loudspeaker and also the use of a single pair of signal wires, thus avoiding the need for multiple wiring for each loudspeaker.
• the choice of directional loudspeakers allows an additional degree of control by permitting adjustment to the polar distribution of the s oundfield produced; this enhances the alarm signal in the preferred direction and minimises its effect in other directions.
• a period timer is provided in order that the duration of the alarm can be pre-set as required to suit the time delay for the specific application.
• a warning system according to the present invention can be designed as a direct replacement of an existing alarm and can be arranged to be operated by the same contact at the main switch panel of the machinery or plant.
• the signal (or tone) generator can be of any suitable design, but is preferably adjustable or programmable.
• the multiplex switching can be operated by frequency or pulse selection, the latter method being preferred if a large number of speakers are used.
• the signals are transmitted to the loudspeakers by wires.
• the invention applies also to other systems, e.g. radio-controlled systems.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Electromagnetism (AREA)
• Emergency Alarm Devices (AREA)
• Alarm Systems (AREA)
• Burglar Alarm Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 1982
  • 1982-02-18 GB GB08229526A patent/GB2107908A/en not_active Withdrawn
  • 1982-02-18 EP EP19820900552 patent/EP0072825A1/en not_active Withdrawn
  • 1982-02-18 AU AU81401/82A patent/AU8140182A/en not_active Abandoned
  • 1982-02-18 JP JP50062882A patent/JPS58500091A/ja active Pending
  • 1982-02-18 WO PCT/GB1982/000042 patent/WO1982002971A1/en not_active Application Discontinuation
  • 1982-10-14 DK DK455582A patent/DK455582A/da not_active Application Discontinuation

Non-Patent Citations (1)

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