Hailers are short range two-way communicators, sort of a cross between a cell phone and a walkie talkie. They can be tuned to specific frequencies, allowing for private chat, but they can also be tuned to public bands that allow hailers to operate as receivers for radio stations such as the one that broadcasts out of the observation deck of the St. Louis Gateway Arch. Some models go even further, acting as a digital recording device and even a low-end scanner. Hailers were initially developed as field radios for the Earth Military Coalition. Their durability has made them indispensible in the new frontier.