The Portable People Meter (PPM) is a system developed by Arbitron to measure how many people are listening (or at least exposed) to individual radio stations and television stations, including cable TV. The PPM is worn like a pager, and detects hidden audio tones within a station or network's audio stream, logging each time it finds such a signal. It has proved to be much more accurate than the old handwritten logs or wired meters, and is immune to forgetful test subjects. There are several parts to the PPM system: The system can also be used for other media, such as movies and music which are recorded with a digital encoding. Various venues and retail locations are also encoding their media in the Houston area. The original concept for the PPM can be traced back to a brainstorming session at Arbitron in November 1988. At that time, concerns over the forthcoming move from analog video to high-definition digital television had engineers concerned that the technology currently in use would become obsolete overnight. Drawing upon his experience in testing labs, Dr. Gerald Cohen proposed embedding an identifying signal in the audio and later decoding it. The rationale was simple. Dr.