Abstract: A communication method and system for providing two-way radio communication links between fixed stations and mobile units, particularly suitable for use in mobile telephone communications. A geographical service area is sectionalized through the use of omnidirectional and directional antennas resulting in increased call capacity for a given number of available communication channels. An orderly, cost-effective manner for accommodating service area expansion, a dynamic channel assignment technique for accommodating variations in user density and a technique for maintaining an established call as a mobile unit moves throughout the sectionalized service area are also disclosed.

Abstract: A mobile communication unit providing simplified calling procedures and thus an increase in the effective use of communication channels. An address signal representing a telephone system subscriber may be entered into a storage register in the mobile unit and the address signal in the register is displayed. A manually depressable call switch is depressed to generate a call initiation signal and a call-up signal including the stored and displayed address signal is broadcast in response to the generation of said call initiation signal through the manual depression of said call switch. A response signal acknowledging said call-up signal is received and receipt of said response signal is automatically indicated. Two-way voice communication is established over a two-way communication channel in response to removal of a handset from cooperating relationship with a hook-switch.

Abstract: A system for controlling the flow of a liquid through a solar heating system of the type having the output of a solar energy collector coupled to the input of a storage tank and having a circulating pump interposed along a return liquid pipe coupled between the recirculating output of the storage tank and the input of the solar energy collector. A first element senses the temperature of the liquid adjacent to the output of the solar energy collector and generates a first signal responsive thereto. A second element senses the temperature of the liquid at a second location within the solar heating system and generates a second signal responsive thereto. A first comparator is coupled between the first and second elements for generating a run signal responsive to the difference between the first and second signals exceeding a predetermined level.