“These “2-bit” radio communicators provide a means to signal each other (as to where they are; if their done …) when shopping at opposite ends of a big box store; even where cell phones have no service or cell battery charge. RFM69 915MHz radio modules are used. They are very efficient radios using digital packet communications. They can communicate over 100 meters using low power, only 10s of miliamps, and as much as 1/2 kilometer or even 1/2 mile using about 120 ma. The units supports a set of, digital, 10-20 (location?) style question and answer codes (refer to wiki/Ten-code https://en.wikipedia.org/wiki/Ten-code ); as well as optional Morse code. The units do not support any voice (analog) communication. They could also be used as pagers with 3 levels of attention requests, when someone is convalescing or working under the house. Beyond that they can be a lot of fun, especially for kids or students.”