The pedestrian crossing, according to the norm, must be equipped with a calling device and a device emitting the go-ahead signal, the whole connected so that, upon a request, the acoustic signal for going-ahead could be issued on both sides of the pedestrian crossing.
The device sends forth 60 sound pulses at first minute, during the green time of the crossing which is connected to, and 120 sound pulses at first minute, during the yellow time. The sound transmission occurs only upon specific request and the transmitting volume is self balanced, during the whole transmitting period, so to conform to the environmental sound level within the whole period.
The sound transmission is in function of the green start of the relevant semaphoric signal, therefore in case of a request made during such period, the request will be fulfilled at the next semaphoric cycle.
Upon each received request, whenever there are such conditions for which the request can be fulfilled, the device will send a signal to the call device in order to send out a sound signal for the accepted request and a signal to the traffic controller for the reservation request of pedestrian green.

TECHNICAL FEATURES

SIGNAL OF ACCEPTED REQUEST TO GO-AHEAD
The above signal has the following characteristics:

• sound frequency = 2KHz ± 10%
• sound pressure level 50 dBA at 1 metre

GO-AHEAD SIGNAL

The above signal has the following characteristics:

• During the Green time:
  • Sound pulses at first minute = 60 ± 1% with duty cycle 50% ± 1%
  • Sound frequency = 800 Hz± 10% modulated at 20 Hz
• During the Yellow time:
  • Sound pulses at first minute =120 ± 1% with duty cycle 50% ± 1%
  • Sound frequency = 800 Hz ± 10% modulated at 20 Hz
• Sound pressure level self balanced in function of environmental rumours:
  • Δ environmental rumours 5÷10 dB
  • Minimum 30 Dba
  • Maximum 60 dBA (according to table B of DPCM 14-11-1997