These are devices very much similar to Geiger Counters both in design and function. They detect particular bands of low level radiation given off by objects that are suffused with significant amounts of V-Gas. Zombies and other organisms which have absorbed enough V-Gas to become animated by the substance have particularly large concentrations of V-Gas and give off radiation in very narrow wavelength bands that can be detected even though significant volumes of solid rock. Such devices are not without their limitations, however. The useful range of the devices in an underground setting is only a few dozen meters. Though V-ger Counters are similar to Geiger Counters, the necessity of using them to locate specific enemy threats and not just background radiation has lead to significant advances. Multi- detector sets have been de-veloped which permit rough triangulation of V-gas sources. These sets are somewhat bulky, but without them, tunnel teams would be at the mercy of the unseen enemy that may lurker around any corner or behind any door. All APE suits have a built-in V-ger counter. Veteran APE pilots still refer to zombies as screechers, wailers, and howlers depending on the size of the group because the old V-ger headset interface pinged zombies like a car passing at speed. The closer the sound seemed, the nearer the target. The signal rose from a background hiss to a static crescendo. The early V-ger interfaces however provided no directional output and have been recently superseded. The newly developed Mono-tech interface emits a clicking noise in the pilot’s headset. If the target is to the right then the right ear clicks, if to the left, then the left ear clicks. Both ears click for ahead. This system also retains the old method that measures proximity and mass by the volume and rapidity of static. Use of Mono-tech is one of the most difficult tasks an APE pilot must master. General Electric R&D teams are working full-tilt to continue to improve the system.