One of the first avalanche beacons to be used was the Skadi, invented by John Lawton in 1968.  It was named after the Norse goddess who traveled on skis, and carried a bow to hunt, but was nicknamed by users as the ‘hot-dog’  for its long and rounded at the edges shape, and of course for its color.  It operated on a 2.275 khz frequency which functioned free from interference and still worked well when blocked by objects. 

The range for the unit was about 30 meters.  The signal got louder when the units got closer together, so by using a grid search pattern a searcher could home in on a buried victim by listening for volume changes.

The Skadi saved lives and was improved upon by European manufacturers.  Popular beacons these days work with a micro-processor and have more functions, but still work the same way.