Background Music System (BMS 1032)
Installation and Operating Manual
FSR
7-6
www.fsrinc.com
AUDIO CALIBRATION
Proper calibration of the BMS system is essential for best performance. The goal of the input trim calibra-
tion is to set the input gain stage to the maximum level before clipping, and to equalize the volume between
all channels. It is at this point that the system delivers the best signal to noise ratio.
All of the source equipment, including any page sources, should be connected to the system before you pro-
ceed. To begin you will need a BMS wall plate, a set of headphones, a cat 5 cable to connect the wall plate
to the rack unit, typical test media to be used with the audio source equipment (tapes, CD’s, etc.), and a small
screwdriver.
Start by setting all the trim pots to the middle of their range. Set the “Max Audio Input #” switch on the left
rear of the rack unit to match the number of the highest input channel connected. For example, if the high-
est audio input used is 4, set the switch to 4. Connect the wall plate to the system using the cat 5 cable, and
plug the headphones in. With all of the sources playing, and the wall plate volume set to a comfortable level,
scan the inputs on the wall plate to find the loudest source. With the loudest source selected, increase the cor-
responding trim control to the maximum level before you hear distortion. Reduce the gain slightly. Make sure
to listen to peaks in the program material for any distortion in order to set the level properly. If you antici-
pate louder media being used in the future, you may want to decrease the gain somewhat to allow for this.
Now scan the channels again to find the quietest source. Increase the trim control on this channel to match
the perceived level of the previously adjusted channel. If the trim pot can’t be set loud enough to achieve
this, simply set it to maximum, and reduce the gain on the previously adjusted channel to match.
Continue in this manner with all remaining audio channels, until they are all adjusted to the same perceived
level. The calibration of the Program Audio Inputs is now complete.
The next step is to calibrate the page audio levels in the system. Start by connecting the actual page audio
source to Page Input 1. With a nominal page signal present, set the Page 1 trim control to be equal to the
music channels. Compare the page level to the music level by turning the page source on and off. If you don’t
hear any paging, either the wall plate is not setup to allow paging (see wall plate setup instructions to enable),
or the Page 1 threshold is set too high (turn threshold pot counterclockwise until the Page 1 Active LED
lights.) Once you have set the Page 1 trim level, you can set the Page 1 threshold level.
The page threshold pot sets the trip level of the automatic page detection circuitry. If it is set too low, it will
false trigger and interrupt the program audio. If it is set too high, the page will not be detected properly and
may cut out during softer portions of a page. Once a page is triggered, it will remain active until page audio
stops for at least 2 seconds. The page hold time pots located inside the rack unit control this time. Consult
the factory if you need to alter this setting.
To set the page threshold level, make sure the page source is connected but inactive. Slowly turn the Page 1
threshold pot CCW until the Page 1 Active LED lights (if the LED does not light, don’t worry, you just have
a good low noise floor.) Note this position. Turn the threshold pot fully CW. Now with the page audio source
active, slowly turn the pot CCW until the LED lights again. Note this position. Set the pot at the mid point
