Apparatus and method for allowing an operator of a transit vehicle to make public address announcements to passengers internal and external to the vehicle. The safety of the vehicle and passengers is maintained through providing a hands-free directional microphone having noise canceling characteristics....http://www.google.fr/patents/US20040240679?utm_source=gb-gplus-shareBrevet US20040240679 - Public address system and method for an urban transit vehicle
Public address system and method for an urban transit vehicle
