Communications: electrical – Pedestrian guidance
Patent
1988-02-01
1989-07-25
Orsino, Joseph A.
Communications: electrical
Pedestrian guidance
340407, G08B 1095
Patent
active
048518360
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to audio-tactile pedestrian push-button signalling systems for use in conjunction with traffic 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 crossings. Two types of audio-tactile signals are provided: locate the push-button assembly and register a demand. This signal is continuously emitted except when the associated 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 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 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: between 20 ms and 30 ms duration; maintain a constant relationship with the instantaneous A-weighted ambient noise level over the range 35 to 75 dB (A); and 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: amplitude square wave having a frequency changing exponentially from 2 kHz to 500 Hz with a time constant of 50 ms; and time constant of 50 ms; and
The tactile signal generated on the front of the push button assembly housing is defined by specification ATS/2 as follows: 30 mm diameter located immediately above the push-button switch, using a pedestrian push-button switch assembly complying with specification No. PB/5. lying between 100 Hz and 175 Hz. 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. (9.81 m/s.sup.2). 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: signal lamps, 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 injectio
REFERENCES:
patent: 2461448 (1948-02-01), Smith
patent: 4253083 (1981-01-01), Imamura
By T. Poulsen, "Acoustic Traffic Signal for Blind Pedestrians", 15 Applied Acoustics 363-376 (1982).
Holst Barrie J.
Wilkinson Barry N.
Amalgamated Wireless Limited
Hofsass Jeffery A.
Orsino Joseph A.
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