SmartSMS User Manual
Soft dB inc.
User Manual
p. 73
External Active Preamplifiers:
The integrated active preamplifier is only able to supply up to 4 sensors. If more sensors are
required, or if the wire length is more than 500 feet, use the SMS-PRE-4 or SMS-PRE-8
preamplifiers.
External preamplifiers have 4 or 8 inputs depending on the model. The signal from the sound level
sensors is averaged and sent to the SmartSMS unit. This method allows a spatial averaging of
the ambient noise. It is recommended to install one Smart sound level sensor for every 1,000
sq. ft. of a given zone to obtain a good representation of the ambient noise in this zone.
Figure 67: Connection of the sensors with an external preamplifier
