Federal Signal AudioMaster 310LD-MV Instrucciones De Instalación Y Servicio página 15

Basic Unbalanced Line System
This configuration is used when hooking to other products on the market.
This system does not offer the same level of noise isolation as a balanced
line system and should only be used when hooking to existing devices.
The neighboring jumpers on the circuit board must be changed from the
BAL position to the UNB position for these installations (see Figure 1).
Figure 11.
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