74158920
Apr 17, 1991
Jan 17, 1995
public messaging system, comprised of a message generator; namely, EEPROMs (electrically erasable, programable, read-only memory) which contain previously recorded messages in digitized form, memory modules, input/output interface module, operator control panels (including keypads, microphones, and monitor speakers), power module, amplifier module, and output speakers which stores, reconstructs and broadcasts digitized speech in mass transit environments
Electrical and Scientific Apparatus