Abstract: A transmitting and receiving system having two or more radios, each capable of transmitting and receiving a transmission signal on two or more radio frequencies where a first radio transmits on a selected frequency at a predetermined time interval and a second radio recovers the transmitted signal. The second radio has a first intermediate frequency generator which generates an intermediate frequency signal which is substantially equal to an integer multiple of the channel spacing whereby an image response corresponding to the selected frequency is separated by twice the intermediate frequency signal from the selected frequency. Thus, locations for the two or more transmission frequencies can be selected so as not to be located on the image responses corresponding to any and all of the two or more transmission frequencies.

Abstract: An alternative power supply apparatus for use in association with systems having a base unit connected to an external power supply and an associated battery-powered portable unit. The alternative power supply apparatus includes two rechargeable batteries one of which serves to provide electrical power to the portable unit. There are two ports associated with the base unit, each port operably and detachably accepts one of the two rechargeable batteries. The apparatus further includes a voltage regulator which provides regulated voltage to circuitry in the base unit. Two current sources each associated with a respective one of the two ports provides an electrical current to the batteries when they are operably accepted by the ports. The second rechargeable battery, which is interchangeable with the first rechargeable battery, provides a source voltage to the voltage regulator upon failure of the external power supply.

Abstract: A voltage regulator apparatus for regulating an unregulated voltage supply to in turn provide a regulated voltage. The voltage regulator apparatus includes a pass device, which has a control port, passes a portion of an unregulated voltage through to the regulated voltage output. The apparatus also includes a DC amplifier which provides a large closed loop gain to the regulated voltage output which is fed back to the pass device control port. The portion of the unregulated voltage passed to the regulated voltage output is a function of the output of the DC amplifier. The apparatus finally includes a voltage reference which provides a reference voltage to the DC amplifier. The DC amplifier voltage reference and pass device control port all draw the same operating current from the unregulated voltage supply. Thus, creating a sharp low-drop out characteristic for the voltage regulator apparatus.