AUDIO-TACTILE PEDESTRIAN PUSH BUTTON SIGNALLING SYSTEM

Abstract: An audio-tactile pedestrian signalling system for use in conjunction with traffic control signal installation having a transducer (16) providing audio and tactile signals by means of signal generator (11, 12, 13, 14). The transducer acts as a microphone to provide a feedback signal to an automatic gain control circuit (19) to adjust the signal to noise level ratio with respect to ambient traffic noise.

Description: AUDIO-TACTILE PEDESTRIAN PUSH BUTTON SIGNALLING SYSTEM ≠ FIELD OF INVENTION This invention relates to audio-tactile pedestrian push- button signalling systems for use in conjunction with traffic 5 control signal installations. BACKGROUND ART An audio-tactile traffic signalling system provides combined audible and tactile signals to supplement the normal pedestrian light signals at controlled pedestrian 10 crossings. Two types of audio-tactile signals are provided:- a) a locating signal which enables the visually handicapped person to locate the push-button assembly and register a demand. This signal is continuously emitted except when the associated 15 pedestrian light signal is green, b) a crossing signal which is emitted only when the associated pedestrian light signal is green. The tranducer for the audio-tactile signal is located 20 within the push-button assembly and acts on the front surface . of the push-button housing. The associated electronic equipment to drive the tranducer is contained in a separate housing remote from the push-button assembly, for example, adjacent to the traffic lights. The remote driver unit or 25 housing is hard-wired to the transducer in the push-button assembly. The audible locating signal as defined by the Department of Main Road of New South Wales, Australia specification ATS/2 has the following operational characteristics:- a) a fundamental frequency within the range 900Hz to 1100 Hz; b) a spectral bandwidth extending to at least 5 kHz; c) a rectangular waveform with a rectangular modulation envelope of between 20 ms and 30 ms duration; d) a pulse repetition frequency within the range of 0.5 to 0.6 Hz; e) an output sound pressure level which is automatically adjusted to maintain a constant relationship with the instantaneous A-weighted ambient noise level over the range 35 to 75 dB (A); and f) fixed upper and lower output sound pressure levels which are maintained when the ambient noise is outside the range specified in (e) above. In order to comply with requirement (e), a microphone is mounted within the remote driver unit or housing to monitor the ambient noise level and to provide a suitable control signal. The audible crossing signal as defined by the above specification ATS/2 has two separate stages:- a) an initial transition stage comprising a single pulse of a constant amplitude square wave having a frequency changing exponentially from 2 kHz to 500 Hz with a time constant of 50 ms; and b) a second stage having the following operational characteristics:- i) a fundamental frequency of between 400 Hz and 600 Hz; ii) a spectral bandwidth extending to at least 5 kHz; iii) a sinusoidal waveform with an amplitude decaying exponentially with a time constant of 50 ms; and iv) a pulse repetition frequency within the range 8 Hz to 10 Hz. The tactile signal generated on the front of the push button assembly housing is defined by specification ATS/2 as follows:- a) the area over which the tactile signal is generated shall be at least 30 mm diameter located immediately above the push-button switch, using a pedestrian push-button switch assembly complying with specification No. PB/5. b) the tactile signal shall have a sinusoidal waveform with a frequency lying between 100 Hz and 175 Hz. c) the tactile signal shall be in-phase with the audible signals specified under Clauses 3.2 and 3.3. The signal shall comprise an integral number of cycles (between 3 and 8) commencing and finishing on a zero crossing, with a duration of not less than 30 milliseconds and periodicity corresponding to the audible signal. d) the tactile signal output shall have a peak acceleration exceeding 1 g (9.81 m/s ) . This will necessitate an output voltage in the range 8 to 11 V peak-to-peak, depending upon frequency, for the nominal sensitivity of the transducer specified in Fig. 2. The remote driver unit or housing contains two isolating transformers connected to:- a) a nominal 240 volt AC mains supply, and, b) the nominal 240 volt AC active feed to the associated pedestrian green signal lamps, for operation of the audio-tactile tranducer as well as the associated electronic circuits. Although the Applicant's prior art audio-tactile traffic signalling system of the kind described above has achieved wide commercial acceptance, there is a need for an improved system which is simpler in constructional detail and cheaper to produce. DISCLOSURE OF INVENTION An audio-tactile pedestrian push-button signalling system according to the present invention includes a housing, signal generator means having an Automatic Gain Control circuit within the housing, a tranducer within the housing operative under the control of the signal generating means to produce pre-determined audio and tactile signals, said transducer being adapted to act as a responsive microphone so as to provide a feedback signal to the Automatic Gain Control circuit for adjusting the signal to noise level ratio with respect to ambient traffic noise. The mounting of the signal generator means and the transducer within the pedestrian push-button housing obviates the need for an additional driver unit or housing as is required by prior art systems. Line tranformers may be mounted within the associated pedestrian signal lanterns which would be advantageous in that it would segregate the low voltage and extra low voltage levels. In a preferred form of the invention, the push-button housing and actuator are manufactured by injection moulding techniques from high grade engineering plastics such as polycarbonate or glass-filled nylon. The use of an injected moulded housing obviates the need for machining, degreasing and painting as is the case with the current aluminium cast housing. The signal generator means incorporates thick film hybrid micro electronics which reduces the area required to house the electronic circuitry so it may be located within the pedestrian push-button rather than in a separate driver unit housing. A compact signal tranducer is designed to produce the correct audible and tactile signals at the appropriate levels. The transducer also acts as a responsive microphone and is capable of providing the required feed-back to operate the Automatic Gain Control circuit so as to adjust the signal to noise level ratio with respect to ambient traffic noise. Such a tranducer eliminates the need for the microphone used in present audio-tactile signalling systems. The audio-tactile signal generator system is driven by a single line transformer which is mounted within the associated pedestrian signal lantern. The input to the signal generator is so arranged, and the line transformer so switched, to differentiate via half and full wave alternating current switching in order to produce the locating and crossing signals with full failsafe backup. The audio-tactile signal generator also produces a visual indication to the pedestrian, to advise that the button has been previously pressed and the crossing signal (as movement) will be serviced by the controller in cyclic order. BRIEF DESCRIPTION OF THE DRAWING In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawing which is a schematic diagram of a signal system for an audio-tactile pedestrian push-button according to an embodiment of the invention. BEST MODE OF CARRYING OUT THE INVENTION The signalling system shown in the drawing includes a main timing network 10 which controls four separate tone generators namely:- (a) WALK tone generator 11 which is adapted to produce a 500 Hz decaying sinewave, (b) DON'T WALK tone generator 12 which is adapted to produce 32 cycles of a 1 kHz square wave, (c) CHANGE tone generator 13 which is adapted to produce a square wave burst starting at about 2 kHz and dropping to 500 Hz over a 50 millisecond period, (d) TACTILE tone generator 14 which is adapted to produce 4 cycles of a 128 Hz sinewave. The output of each of the tone generators 11,12,13 and 14 is applied to power amplifier 15 which drives the transducer 16. The main power supply unit 17 is remote from the transducer 16, being either at the top of the traffic light pole (not shown) or at the main control box (also not shown) for the system. The power supply unit 17 provides an extra low A.C. votage which is half wave during the DON'T WALK mode and full wave during the WALK mode. Thus, only two wires are needed to power and control the system. The local power supply unit 18 within the pedestrian push-button housing rectifies the A.C. signal from the power supply unit 17 to provide the D.C. voltages required. The local power supply unit 18 also decodes the full wave/half wave signal to provide the WALK and DON'T WALK signals to the main timing network 10. The sound transducer 16 is constituted by the circular aluminium plate normally used in the push-button assembly as the direction arrow indicator. The transducer 16 is vibrated by a loudspeaker style magnet and voice coil assembly. The transducer 16 is also used as the microphone for the automatic volume control in the DON'T WALK mode. The power amplifier 15 has an output DISABLE control to allow the transducer 16 to be used as the microphone during the time between pulses in the DON'T WALK signal. The microphone output of the transducer 16 is applied to amplifier/rectifier 19 to give a D.C. signal which automatically controls the gain of the DON'T WALK signal. The network 10 has a disable control to prevent it from being swamped by the power amplifier when it is active. The tone generators 11,12,13 and 14 are controlled by the main timing circuit 10 so that in the DON'T WALK, mode the tactile tone is repeated every 2 seconds followed immediately by the DON'T WALK tone burst to provide an audible locating signal and a slow tactile signal indicating not to walk. When the WALK light comes on, the CHANGE tone sounds once to attract attention and then the WALK tone is repeated eight times per second. The difference in tone and repetition rate gives the audible WALK signal while the high level tone acts as the tactile component with the repetition rate being the determining factor. Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

Claims: CLAIMS 1. An audio-tactile pedestrian push-button signalling system comprising signal generator means having an automatic gain control circuit, a transducer operative under the control of the signal generator means to produce pre¬ determined audio and-tactile signals, said transducer being adapted to act as a responsive microphone so as to provide a feedback signal to the automatic gain control circuit for adjusting the signal to noise level ratio with respect to ambient traffic noise. 2. A signalling system according to claim 1 wherein the system is driven by a single line operative to provide a first mode of signal representing a WALK signal and a second mode of signal representing a DON'T WALK signal. 3. A signalling system according to claim 2 and further including a timing network driven by the first and second modes to actuate, in a predetermined manner, the signal generator means to provide WALK, CHANGE and DON'T WALK tones as well as tactile signals. 4. A signalling system according to claim 3 and further including a power amplifier coupling the signal generator means to the transducer. 5. A signalling system according to any one of claims 2 to 4 and including a power supply circuit connected between the single line driver and the signal generator means operative to decode the first and second signal modes to provide WALK and DON'T WALK signals to the signal generator means, 6. A signalling system according to any one of claims 2 to 5 wherein the first signal mode is a half wave signal and the second signal mode is a full wave signal. 7. A signalling system according to claim 4 and including means to limit the operation of the transducer as a microphone to the time between pulses in the DON'T WALK signal. 8. A signalling system according to any one of claims 1 to 7 wherein the transducer is coupled to the signal generating means through an amplifier rectifier. 9. A signalling system according to claim 3 wherein the timing circuit is arranged to provide, in the DON'T WALK mode, a tactile tone which is repeated on a regular basis followed by a DON'T WALK tone burst to provide an audible locating signal and a slow tactile. 10. A signalling system according to claim 9 wherein the timing circuit is arranged to provide the CHANGE tone when the WALK signal is generated followed by the WALK tone repeated on a regular basis, the difference in tone and repitition rate giving the audible WALK signal while the high level tone acts as the tactile component.

Inventors: HOLST BARRIE JAMES, WILKINSON BARRY NORMAN, HOLST, BARRIE, JAMES, WILKINSON, BARRY, NORMAN
Applicants: AMALGAMATED WIRELESS AUSTRALAS, AMALGAMATED WIRELESS (AUSTRALASIA) LIMITED
Application year: 1987
Main classification: G08G1
IPC codes: F02B75, G08G1, G09B21