Automatic equalization for a simulcast communication system

A simulcast communication system, comprising:

• a plurality of base stations for simultaneously broadcasting an audio signal;
• a dispatch station for transmitting said audio signal to said base stations along telephone lines;
• pilot signal means associated with said dispatch station for generating a pilot signal to be transmitted to each of said base stations with said audio signal;
• phasing signal means associated with said dispatch station for generating a phasing signal to be transmitted to each of said base stations prior to said audio signal;
• detection means associated with each of said base stations for detecting said pilot signal, and for detecting the occurrence of said pushing signal;
• and
• synchronizing means associated with each of said base stations and responsive to said detected pilot and phasing signals, for generating a substantially synchronized squelch signal at each of said base stations.

In a communication system having a plurality of base stations, a dispatch station, and a receiver associated with said dispatch station, automatic equalization means for enabling an audio signal transmitted from said dispatch station to each of said base stations along telephone lines to be simultaneously broadcasted from said base stations, comprising:

• first circuit means associated with said dispatch station for substantially equalizing the audio transmission characteristics from said dispatch station to each of said base stations in response to at least one test signal which is sequentially transmitted from said dispatch station to each of said base stations, broadcasted from each of said base stations, and received at said dispatch station by said receiver;
• and
• second circuit means for generating a substantially synchronized squelch signal at each of said base stations in response to a pilot signal and a phasing signal;
• said dispatch station transmitting said pilot signal to each of said base stations with said equalized audio signal and said phasing signal to each of said base stations prior to said equalized audio signal.

A method of equalizing the audio signal transmission characteristics from a dispatch station to a plurality of base stations in a communication system where said audio signal is transmitted from said dispatch station to each of said base stations along telephone lines, comprising the steps of:

• generating test signals and transmitting said test signals from said dispatch station to said base stations in a predetermined sequence;
• broadcasting said transmitted test signals from said base stations in said predetermined sequence;
• receiving test response signals, each of which represents a test signal broadcasted from one of said base stations;
• determining the audio signal transmission characteristics required to equalize the audio signal transmission characteristics from said dispatch station to each of said base stations from said test response signals;
• and
• adjusting the audio signal transmission characteristics from said dispatch station to at least one of said base stations in order to equalize the audio signal transmission characteristics from said dispatch station.

A method of generating a synchronized squelch signal to be simultaneously broadcasted from a plurality of base stations in a communication system where an audio signal is transmitted from a dispatch station to each of said base stations along telephone lines, comprising the steps of:

• generating a pilot signal and transmitting said pilot signal to each of said base stations with said audio signal;
• generating a phasing signal and transmitting said phasing signal to each of said base stations at the beginning of said audio signal;
• and
• generating a substantially synchronized squelch signal at each of said base stations in response to said pilot and phasing signals.

A simulcast communication system, comprising:

• a plurality of base stations for simultaneously broadcasting an audio signal;
• a dispatch station for transmitting said audio signal to said base stations along telephone lines;
• test signal means for generating at least one test signal to be transmitted from said dispatch station to each of said base stations in a predetermined sequence;
• receiver means for receiving test response signals, each of said test response signals representing a test signal broadcasted from one of said base stations;
• digital processing means for determining the audio signal transmission characteristics required to equalize each of said base stations from said test response signals;
• and
• programmable equalization means for substantially equalizing the audio signal transmission characteristics from said dispatch station to each of said base stations in response to said digital processing means, wherein one of said base stations is designated as a reference base station and the audio signal transmission characteristics from said dispatch station to the other of said base stations are equalized to the audio signal transmission characteristics from said dispatch station to said reference base station.