New Delhi, Feb. 15 -- Authorities searching for Nancy Guthrie are deploying a piece of specialized tracking technology - commonly referred to as a "signal sniffer" - in an effort to detect emissions from her implanted pacemaker as the investigation intensifies in Tucson, Arizona.

Here's what that device is - and how it works.

A signal sniffer is a radio-frequency (RF) detection device used to locate electronic signals emitted by wireless equipment. Law enforcement and search teams typically use such technology to:

-Detect radio transmissions

-Identify wireless communication devices

-Track signal sources within a defined range

In this case, authorities mounted the device on a helicopter operated by the Pima County Sheriff's Departmen...