Abstract: A very rapidly converging adaptive filter which uses a variable scale factor for each weight of the filter. The value of the variable scale factor is chosen for each iteration and is based upon the sign changes of the incremental weight change. The variable scale factor exhibits large values when no sign changes occur and smaller values when sign changes occur. The new filter provides considerable improvement in increase of convergence rate and decrease in residual errors even in the presence of heavy noise while requiring only a modest increase in hardware.

Abstract: A siren alarm on an emergency vehicle or a like warning vehicle, for transmission forwardly over a limited range along the vehicle path, of a broadcast band carrier wave modulated with a siren signal with break-in possible for voice modulation of the carrier, with the carrier frequency rapidly and continuously repeatedly swept over the broadcast frequency band, both in the AM broadcast band and FM broadcast band, thereby to produce in other vehicles, having standard broadcast radio receivers in operation, a warning signal or voice communication; optionally with warning vehicle speed responsive control of the transmitter output power for establishing a transmission range proportional to the warning vehicle speed.