Method and apparatus for multiplexing switch signals
US4884070A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 4, 1988 |
| Grant date | Nov 28, 1989 |
| Priority date | — |
| Expiry date | Apr 4, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M11/24
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Apparatus for multiplexing switch state signals comprises a plurality of switches and parallel weighted resistors connected in series between circuit ground and a node at a utilization device. The resistors are weighted as a function of a power of the same base, such as the power of the base 2, for coding the multiplexed switch state signals. A constant current source connected between the node and circuit ground drives current over a single cable conductor through the resistor. Each switch may be independently closed to change the switch state voltage signals multiplexed to the node. An analog-to-digital converter connected between the node and circuit ground demultiplexes the switch state signals received at the node and provides a switch state signal at each analog-to-digital output corresponding to the state of the switches at the moment. A potentiometer may replace a resistor and bypass switch combination in a position where the potentiometer has a maximum value of the lowest power of the base in order to multiplex a true analog voltage signal while switch state signals are unambiguously coded and multiplexed. The potentiometer in the least significant position permits the ana…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.