EP1174835A2 - Systèmes d'avertissement audible - Google Patents

Systèmes d'avertissement audible Download PDF

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Publication number
EP1174835A2
EP1174835A2 EP01305973A EP01305973A EP1174835A2 EP 1174835 A2 EP1174835 A2 EP 1174835A2 EP 01305973 A EP01305973 A EP 01305973A EP 01305973 A EP01305973 A EP 01305973A EP 1174835 A2 EP1174835 A2 EP 1174835A2
Authority
EP
European Patent Office
Prior art keywords
frequency
transducer
output
periods
audible
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01305973A
Other languages
German (de)
English (en)
Other versions
EP1174835A3 (fr
Inventor
John Lewinsky
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RAFIKI HOLDINGS Ltd
Original Assignee
Rafiki Protection Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rafiki Protection Ltd filed Critical Rafiki Protection Ltd
Publication of EP1174835A2 publication Critical patent/EP1174835A2/fr
Publication of EP1174835A3 publication Critical patent/EP1174835A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B3/00—Audible signalling systems, e.g. audible personal calling systems
    • G08B3/10—Audible signalling systems, e.g. audible personal calling systems using electric transmission; using electromagnetic transmission

Definitions

  • This invention relates to audible warning devices and more particularly but not solely to audible warning devices for alarm systems.
  • Audible warning devices which comprise an audible transducer such as a loudspeaker or piezo transducer and a driver circuit which applies an alternating voltage to the transducer thereby causing the transducer to output an audible signal at the frequency of the applied voltage. It is often a characteristic of such transducers and their associated components that the outlet level according to the frequency of the applied voltage.
  • the output frequency of the warning signal generated by the devices is in the range of 500-1000Hz.
  • a disadvantage of this is that the output level of the transducers used in the devices is often low when the transducers are driven with an alternating voltage in this frequency range.
  • an audible warning device arranged to generate an audible output signal having a first frequency
  • the device comprising an audible output transducer and a driver circuit for applying an alternating drive signal, having a second and higher frequency, to the transducer over successive distinct periods, the frequency of the periods being equal to said first frequency
  • the transducer can be driven by an alternating voltage having a frequency equal to a frequency at which the output of the transducer would normally be high.
  • the alternating voltage is only applied in successive distinct periods of a lower frequency, the transducer appears to produce an output signal at this lower frequency.
  • the device is able to meet the requirements for a fire alarm system but yet produces a high output level.
  • the driver circuit outputs successive groups of positive or negative going pulses at said first lower frequency, the pulses being output at said second higher frequency.
  • the driver circuit outputs successive groups of successive positive and negative going pulses at said first lower frequency, the pulses being output at twice said second higher frequency.
  • the successive positive or negative going pulses in the group are output at the second higher frequency.
  • Driving the transducer with successive positive and negative going pulses helps to establish rapid oscillations at resonant frequency in an inductive transducer connected as a part of a tuned circuit.
  • a method of maximising the sound output level of an audible warning device at a desired frequency comprising the steps of:
  • FIG. 1 of the drawings there is shown an audible warning device of the type used in a fire alarm system to warn when an alarm condition is triggered.
  • the device comprises an audible transducer 10 of the type disclosed in British patent application No. 2 106 748 having an inductive coil L which vibrates an armature when an alternating electric current is passed therethrough.
  • the coil L is connected across a capacitor C to form a tuned circuit.
  • the upper arm of the tuned circuit is connected to the positive voltage rail +v and its lower arm is connected to the zero volts rail 0v via a switching device such as an npn bipolar transistor 11.
  • the capacitance value of the tuned circuit is chosen so that the resonant frequency of the circuit is at or near the frequency at which the output of the transducer is known to be high compared with the voltage across the coil L.
  • the actual frequency value at which the maximum sound output is produced varies from transducer to transducer owing to slight differences in mechanical and electrical characteristics.
  • a variable frequency test signal is applied to terminal 13 and the sound output level of the transducer is monitored to determine the frequency at which the output level is maximised. This frequency is recorded and entered into a microprocessor 12 connected to the base of the transistor 11.
  • the microprocessor 12 is also programmed with the desired frequency at which the transducer 10 is to emit sound.
  • the microprocessor 12 outputs a waveform A comprising successive positive and negative going pulses 14,15, with the frequency (1/T2)of the waveform being equal to the determined frequency at which the output level of the transducer 10 is maximised.
  • the pulses 14,15 induce oscillations in the tuned circuit LC, such that a voltage waveform B is applied across the coil L.
  • the microprocessor 12 is arranged to output the waveform A over successive distinct periods, with the frequency (1/T1) of the periods being equal to the desired audio output frequency of the transducer 10.
  • the microprocessor may vary the frequency (1/T1) at which the groups of pulses are emitted, so that a sweeping or pulsed audio output signal is generated.
  • the width of the generated pulsed 14,15 may be varied to vary the amount of power delivered to the transducer.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Fire Alarms (AREA)
  • Alarm Systems (AREA)
EP01305973A 2000-07-18 2001-07-11 Systèmes d'avertissement audible Withdrawn EP1174835A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0017477A GB2368997B (en) 2000-07-18 2000-07-18 Audible warning devices
GB0017477 2000-07-18

Publications (2)

Publication Number Publication Date
EP1174835A2 true EP1174835A2 (fr) 2002-01-23
EP1174835A3 EP1174835A3 (fr) 2003-03-05

Family

ID=9895779

Family Applications (1)

Application Number Title Priority Date Filing Date
EP01305973A Withdrawn EP1174835A3 (fr) 2000-07-18 2001-07-11 Systèmes d'avertissement audible

Country Status (2)

Country Link
EP (1) EP1174835A3 (fr)
GB (1) GB2368997B (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1507603A1 (fr) 2002-05-23 2005-02-23 Gent Limited Alarme acoustique dotee d'un element piezo-electrique actionne a plusieurs frequences
US7369061B1 (en) * 2004-10-05 2008-05-06 Steven Sellers Vehicle locator device
US20110260875A1 (en) * 2010-04-21 2011-10-27 Koninklijke Philips Electronics, N.V. Alert device and method

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4104628A (en) * 1976-10-15 1978-08-01 P.R. Mallory & Co. Inc. High output audible alarm device utilizing a piezoelectric transducer and voltage doubling means
GB1555538A (en) * 1977-07-05 1979-11-14 Madewel Products Ltd Electronic audio alarm
US4275388A (en) * 1980-01-09 1981-06-23 General Electric Company Piezoelectric audible alarm frequency self-calibration system
JPS57210395A (en) * 1981-06-19 1982-12-23 Ricoh Kk Piezo-electric buzzer driving system
US4401975A (en) * 1981-11-19 1983-08-30 General Signal Corporation Electrical synthesis of mechanical bell
DE3147364A1 (de) * 1981-11-30 1983-06-01 Siemens AG, 1000 Berlin und 8000 München Schaltungsanordnung fuer einen akustischen signalgeber
US4397210A (en) * 1981-12-11 1983-08-09 Cbs Inc. Rhythm sound generator
US5293149A (en) * 1991-04-12 1994-03-08 Sparton Corporation Vehicle horn with electronic solid state energizing circuit
US5414406A (en) * 1992-04-21 1995-05-09 Sparton Corporation Self-tuning vehicle horn

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1507603A1 (fr) 2002-05-23 2005-02-23 Gent Limited Alarme acoustique dotee d'un element piezo-electrique actionne a plusieurs frequences
EP1507603B1 (fr) * 2002-05-23 2014-12-03 Gent Limited Alarme acoustique dotee d'un element piezo-electrique actionne a plusieurs frequences
US7369061B1 (en) * 2004-10-05 2008-05-06 Steven Sellers Vehicle locator device
US20110260875A1 (en) * 2010-04-21 2011-10-27 Koninklijke Philips Electronics, N.V. Alert device and method

Also Published As

Publication number Publication date
GB2368997A (en) 2002-05-15
EP1174835A3 (fr) 2003-03-05
GB2368997B (en) 2005-05-11
GB0017477D0 (en) 2000-08-30

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