Miniature portable public address system

Claim 2

In a motor bus including loud speakers mounted inside the bus, a sound amplifier connected to the speakers, and a DC power supply for providing electrical energy to the amplifier, an improved sound amplifier comprising: a generally rectangular hand-held case having a plurality of first electrical connectors and a plurality of second electrical connectors; transducer means contained within said case for converting sound waves into electrical impulses; amplification means disposed within said case and connected to said transducer means for developing an amplified signal from the electtical impulses, said amplifier means also being connected to said first electrical connectors and including a first transistor and a second transistor in Darlington configuration, and a power amplifier to develop said amplified signal; cable means for connecting said first electrical connectors to the bus's loud speakers and for connecting said second electrical connectors with the bus's power supply; first switch means for connecting said amplification means to said second electrical connectors to allow electric current to flow from the bus's power supply to said amplification means; second switch means for connecting said transducer means to the base of said first transistor; and volume control means connected to said amplification means for determining the magnitude of the amplified signal, said volume control means being mounted to said case and protruding therefrom so as to be externally accessible said sound amplifier being operative to cause sound waves contacting said transducer means to be amplified and broadcast over the motor bus loud speakers.

Claim 3

In a motor bus as recited in claim 1 wherein said case further includes an auxiliary input connector connected to said second switch means and said first and second switch means are ganged together by a three-position rocker actuator having a first position for intermittently allowing electric current to flow from the power supply and transducer means to said amplifier means, a second position for continuously allowing electric current to flow from the power supply and auxiliary input connector to said amplifier means, and a third position for not allowing electric current to flow from the power supply to said amplifier means.

Claim 4

In a motor bus as recited in claim 1 wherein said transducer means inlcudes a crystal microphone.

Claim 5

A public address sytem comprising: electrical power means for providing electrical energy; sound generating means for developing sound in response to an electrical signal; a first case for housing said electrical power means and said sound generating means; a firsft electrical connector passing through said first case and connected to said electrical power means; a second electrical connector passing through said first case and connected to said sound generating means; a second case, generally rectangular in shape; transducer means for converting sound waves into electrical impulses, said transducer means mounted to said second case; amplification means connected to said transducer means for amplifying the electrical impulses into an amplified signal, said amplification means being mounted within said second case and including a first transistor and a second transistor in Darlington configuration and a power amplifier connected to the output of said second transistor; a third electrical connector passing through said second case and having a first group of terminals connected to the power input terminals of said amplification means and a second group of terminals connected to the output terminals of said amplifier; amplification control means connected to said amplification means for controlling the magnitude of the electrical signal, said amplification control means mounted to said second case so as to partially protrude therefrom; cable means for connecting said first electrical connector to said first group terminals and said second electrical connector to said second group terminals; and switch means connected to said amplifier means and said third electrical connector for allowing current to flow from said electrical power means to said amplification means, said switch means mounted to said second case so as to protrude therefrom, whereby sound waves contacting said transducer means are amplified by said amplification means and broadcast by said sound generating means.

Claim 6

A public address sytem comprising: electrical power means for providing electrical energy; sound generating means for developing sound in response to an electrical signal; a first case for housing said electrical power means and said sound generating means; a firsft electrical connector passing through said first case and connected to said electrical power means; a second electrical connector passing through said first case and connected to said sound generating means; a second case, generally rectangular in shape; transducer means for converting sound waves into electrical impulses, said transducer means mounted to said second case; amplification means connected to said transducer means for amplifying the electrical impulses into an amplified signal, said amplification means being mounted within said second case and including a first transistor and a second transistor in Darlington configuration and a power amplifier connected to the output of said second transistor; a third electrical connector passing through said second case and having a first group of terminals connected to the power input terminals of said amplification means and a second group of terminals connected to the output terminals of said amplifier; amplification control means connected to said amplification means for controlling the magnitude of the electrical signal, said amplification control means mounted to said second case so as to partially protrude therefrom; cable means for connecting said first electrical connector to said first group terminals and said second electrical connector to said second group terminals; and switch means connected to said amplifier means and said third electrical connector for allowing current to flow from said electrical power means to said amplification means, said switch means mounted to said second case so as to protrude therefrom, whereby sound waves contacting said transducer means are amplified by said amplification means and broadcast by said sound generating means.

Claim 7

A public address system as recited in claim 4 wherein said electrical power means includes a plurality of dry-cell batteries.

Claim 8

A public address system as recited in claim 4 wherein said electrical power means includes power conversion means for converting AC power into DC power.

Claim 9

A public address system as recited in claim 4 wherein said electrical power means includes means for connection to a vehicular electrical system.

Claim 10

A public address system as recited in claim 4 wherein said switch means includes a multi-position switch having a first, second and third position for intermittent open, continuous open, and continuous closed operation, respectively.