Technical data

Chapter 4: Installation

WARNING: Excessive BGM voltage input can cause amplifier failure. Make

sure that the preferred audio source output for the BGM input of the SP40S panel

(CD player, tuner, equalizer, etc.) is a fixed line level voltage less than 2.5v peak to

peak or 300mv rms. Audio sources marked “line level output” are typically within

this limit. Audio sources with other than fixed line level outputs (that is, adjustable

speaker outputs, etc.) require that the audio source be adjusted using a multi-meter

across the output of the signal source (see below).

Once the level has been set properly, secure the adjustable audio source so that the

level cannot be inadvertently changed. Failure to set adjustable audio sources

appropriately or failure to secure audio adjustable sources can lead to failure of the

amplifier section of the SP40S Panel. This failure, in turn, could result in serious

injury or death to you and/or others.

4.4.10 Setting Adjustable Audio BGM Sources

NOTE: Use a good multi-meter that provides true RMS readings in the AC voltage scale and calculates the

results through average sampling. Some multi-meters can select instant or average sampling readings. Always

do this adjustment in the “averaging” mode. Most digital multi-meters use the average sampling method in the

“AC Volts RMS” setting.

1. Ensure that power is disconnected from the SP40S panel.

2. Set the Audio Source volume control to the minimum setting.

3. Connect the Audio Source output to the BGM input terminals (TB5) on the panel.

4. Set the multi-meter to the AC Volts scale, which is capable of reading 300mV RMS.

5. Connect the multi-meter across the BGM terminals on the panel.

6. Adjust the output control of the audio source to obtain a reading of 300mV RMS on the multi-meter.

7. Secure the output control of the audio source so that it cannot be changed inadvertently.

8. Disconnect the multi-meter. The output of the Audio Source is now correctly set for the SP40S BGM

input.

SP40S Multi-Function Facility Communication System Manual, Revision D