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3
Option 1: Ring the front doorbell of the IS7121 and existing wired
doorbell simultaneously.
Using another wire, slide one end of the metal part underneath the
metallic plate on the doorbell, then connect the other end to the
Trans terminal of your chime/buzzer unit of the wired doorbell.
4.
Chime/buzzer of
wired doorbell
Transformer
Rear
Trans
Front