One panel with dual output voltage (example: 120vac / 120vac or 208vac / 120vac), one or two breaker panel(s), and two line isolation monitors (LIM) with the same test frequency – usually two LIMs of the same make and model. 

When testing the line for leakage to ground, the line isolation monitor emits a low-level frequency. This is normal. However, when (2) LIMs with the same test frequency are in the same panel near each other, their test frequencies will be detected by the other LIM causing inaccurate, erratic readings or even alarms in one or both LIMs. 

Typically, one of the LIMs would be replaced by a different model having a different test frequency. However, the new Sentry 5 LIM is equipped with a “dip switch” preset to switch A. When two Sentry 5 LIMs or one Sentry 5 LIM and another model with the same frequency are near each other, one Sentry 5 LIM can be set to switch B resulting in unique frequencies. 

Switch 4 is the only switch that needs to be changed. First, remove the cover plate as indicated in figure 1. Locate the dip switch as shown in figure 2 and change switch 4 from Off to On. This changes the LIM frequency. Replace the cover plate.