Addressable transducer with a variable frequency oscillation for monitoring a physical quantity
US4399440A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 17, 1981 |
| Grant date | Aug 16, 1983 |
| Priority date | — |
| Expiry date | Feb 17, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/28
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An addressable transducer is disclosed for use in monitoring the values of physical conditions in connection with long electric lines, such as telephone cables. Multiple transducers are connected across a single pair of transmission lines which extend from a central station and supply a DC voltage to the transducers. Each transducer has an assigned address in the form of a binary code. An address signal is transmitted on the transmission lines by pulse width modulation of the line voltage. An address detector converts the address to a binary code and the transmitted address is compared with the assigned address. When the assigned address is received, a variable frequency current sink oscillator is turned on and connected across the lines. The oscillator has a frequency determined by a sensor responsive to the physical condition being measured and modulates the line current at that frequency. The frequency of the line current modulation is measured at the central station and represents the value of the physical condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.