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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2012 Oct 20;199(1):57–69. doi: 10.1007/s00359-012-0768-4

Figure 2.

Figure 2

Schematic of the custom-built collar system consisting of a Hall-effect transducer mounted on a non-magnetic ring. The ring was attached on the back of the head. A small piece of rare earth magnet was mounted on the skin above the larynx. If OEC was enlarged, the magnet moved towards the transducer and thereby caused a voltage change, which reflects the change in distance between the magnet piece and the Hall-effect transducer.