Modem compression system for telephone network
US4805208A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 15, 1988 |
| Grant date | Feb 14, 1989 |
| Priority date | — |
| Expiry date | Jan 15, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L1/206
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Bit compression system for a telephone modem utilizing differential phase shift modulation of a low-frequency tone carrier to transmit dibit or tribit values. Instead of transmitting digitized samples of the tone carrier over a conventional T1 telephone network, the modem compression system tribit extracts the dibit or values from digitized samples of the tone carrier, and transmits assembled T1 data bytes in a data stream containing solely the data bits encoded by the modem. At the receiving end, a modem decompressor reconstructs the digitized samples of the tone carrier using the dibit or tribit values. The T1 telephone network then uses the reconstructed digitized samples to reproduce the analog tone carrier for the receiving modem. The modem compressing system also includes AGC circuit for normalizing the levels of the T1 data samples and a modem/voice data detector for alternately routing the T1 data samples to respective speech and modem compressors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.