Site controller with echo suppression
US5357609A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 25, 1992 |
| Grant date | Oct 18, 1994 |
| Priority date | — |
| Expiry date | Mar 25, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B3/20
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An embodiment of the present invention is a site controller that comprises a microcomputer with a RAM for main memory and an EPROM for program memory, an interface for accepting RS-485 data and voice communication on respective differential wire pairs from a daisy chain of student response keypad terminals, a public telephone data access arrangement with hybrid for sending and receiving voice over a dial-up line, a universal asynchronous receiver-transmitter for data communication by modem with a remote host site via an X.25 PAD and an audio processor for half-duplex communication between an instructor and a student that has voltage controlled amplifiers and side chain devices that reduce audio amplifier gain during periods of silence in order to eliminate feedback howl and adjustable delay and threshold devices for gating the respective channels through in the half-duplex mode.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.