초록 ▼

An automatic reorder and alarm system for use with residential fuel-oil tanks which sends reorder and alarm data to a central station over the direct-dial telephone network when the fuel-oil level in the tank falls below a predetermined value or when an alarm situation, such as low temperature, occu

An automatic reorder and alarm system for use with residential fuel-oil tanks which sends reorder and alarm data to a central station over the direct-dial telephone network when the fuel-oil level in the tank falls below a predetermined value or when an alarm situation, such as low temperature, occurs at the tank location. An inexpensive sensor/sending unit located at each customer tank includes a simple sensor which mounts on either the tank or an existing fuel-oil level gauge, a microcontroller circuit and a modem circuit. The microcontroller circuit uses a simple low-stability oscillator as a reference for internal operations and for modem transmission frequencies. Because the oscillator frequency cannot be precisely determined due to component tolerances and has a substantial amount of drift, a special data transmission format is used for data transmission over the telephone lines between the microcontroller and the central station. The data format consists of a selected pattern of mark and space signals in which each mark signal consists of a predetermined number of cycles of an oscillating signal whose frequency is determined by the internal modem oscillator and each space signal is an equivalent time period without a signal. At the receiver the bit time duration is determined by averaging bit times in a predetermined bit pattern header.

대표청구항 ▼

In a system for reporting a fuel-oil level in a residential tank to a central location, a sensor unit located near said tank, said sensor unit comprising: means located near said tank for generating a fuel-oil level sense signal, detector means responsive to said sense signal for producing a reorder

In a system for reporting a fuel-oil level in a residential tank to a central location, a sensor unit located near said tank, said sensor unit comprising: means located near said tank for generating a fuel-oil level sense signal, detector means responsive to said sense signal for producing a reorder signal when the fuel-oil in said tank reaches a predetermined level, an oscillator for generating an output signal, said output signal having a frequency variation, and controller means responsive to said reorder signal and to said output signal for transmitting a data word encoded by digital bits consisting of pulses of said output signal to said central location, said data word comprising a fixed, predetermined header pattern of bits, followed by a plurality of data bits including at least one bit indicating the status of said reorder signal and a plurality of identification number bits, said identification number bits representing an identification number unique to said sensor unit, followed by a checksum code bit pattern encoding a checksum derived by logically combining said identification number bits with each other.