Daisy chainable voice-data terminal
US5329620A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 25, 1992 |
| Grant date | Jul 12, 1994 |
| Priority date | — |
| Expiry date | Mar 25, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09B5/14
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A daisy chain voice-data terminal for communicating data and voice signals between remote locations, comprising, according to an embodiment of the present invention, a microcomputer with a RAM for main memory and an EPROM for program memory, a membrane keypad connected to an input port of the microcomputer, a liquid crystal display adjacent to the keypad and connected to an output port of the microcomputer, a microphone and preamplifier, a differential output audio amplifier, a relay controlled by the microcomputer to switch the differential output audio amplifier on and off a daisy chain cable connected to other response keypads and a site controller, an RS-485 serial input/output to interface the microcomputer to the daisy chain cable, a switching regulator to provide five volts to the logic circuits, and a separate three-terminal linear regulator to supply five volts to the audio circuits. At each response keypad, the wiring for the audio channel is cross connected to balance out any noise that may be otherwise induced in the audio signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.