The accompanying article doesn’t specify, but since this picture was taken in 1938, I assume that the horse had a 6 volt electrical system, rather than the more modern 12 volt. But in any event, the mounted British police officer can stay in touch with headquarters or other squad cars thanks to this portable two-way radio.

The officer was on duty at the Grand National steeplechase, where the new radios were introduced. The photo appeared in the July 1938 issue of Popular Science.