# Changing reference sensor location

EPOC X comes shipped with rubber comfort pads set at the mastoid sensor locations as default. Which means the default referencing in EPOCX devices is P3/P4 referencing. Please see image below as reference.

![](/files/klqUiMHsqY4a3tVLnWl8)

EPOC X can be operated with the rubber comfort pads in the M1/M2 sensor positions, as well as the P3/P4 positions. To switch to mastoid referencing from the default, take the rubber pads out from the M1/M2 sensors and insert them into P3/P4 sensor positions. Ensure wet felt pads on all other sensors including M1/M2 to ensure mastoid referencing. Please see image below as reference.

![](/files/eZ8YgAoHo0ihD87tyYjK)

You can change the configuration of the reference sensors at any time between recordings, whilst they are not in use. The rubber pads can be removed by twisting them out in the same way that the felt sensors can be twisted out. Simply remove them in this fashion from their existing positions, and insert them into the desired positions.


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