Residential fuel-oil level reporting and alarm system
US4845486A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 12, 1986 |
| Grant date | Jul 4, 1989 |
| Priority date | — |
| Expiry date | Sep 12, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/002
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
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 si…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.