发明名称 |
Residential fuel-oil level reporting and alarm system |
摘要 |
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.
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申请公布号 |
US4845486(A) |
申请公布日期 |
1989.07.04 |
申请号 |
US19860907120 |
申请日期 |
1986.09.12 |
申请人 |
SCULLY, ROBERT |
发明人 |
KNIGHT, JOHN D.;SHAPIRO, ROBERT D.;BANKS, FRANK H.;MITCHELL, ANDREW;SUNRAY, BARRY S.;DEFRANCESCO, ROBERT A. |
分类号 |
G01F23/36;H04M11/00 |
主分类号 |
G01F23/36 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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