A hundred years ago, the U.S. Forest Service had the latest in portable telephones, as shown in the July 1919 issue of Popular Science.

This ranger is shown carrying the set, which weighs in at a featherweight 30 pounds. The bottom compartment contains the batteries, with the normal telephone transmitter and receiver in the top compartment. A magneto is included to ring the phone. Upon spotting a fire, the ranger races to the nearest phone line and hooks up the instrument. He gives the magneto a turn, which alerts the other phones on the line, and the fire gets reported.

But what if the other rangers have stepped out away from the phone? That’s where the middle shelf comes in. It contains a loud klaxon which would echo through the forest. If there’s no answer, the ranger switches the dynamo to DC to drive the klaxon and gives it another spin. The sound is presumably heard for miles around, his colleagues pick up the phone, and the fire gets reported.