| 摘要 |
<p>A multipurpose sound communication system for use anywhere. This system may thus be used in a number of ways not described in the specification, but will be found useful in many, if not all, emergency vehicles including, but not limited to, ambulances and police patrol cars. The system employs one voltage controlled oscillator (VCO) with six selectively adjustable inputs. One of the inputs if OFF. Three inputs provide different corresponding siren sounds. One input places the radio on the speaker. Another input provides for public address and manual control of the siren. Speaker assembly negative feedbacks are provided for signal balance. Two negative feedbacks are selectively provided. A manual control circuit provides ramp voltages for siren control through the VCO. A transistor switch is driven to cut-off to prevent VCO operation when the siren frequency falls below a predetermined frequency.</p> |
