H - Electricity – 04 – M
Patent
H - Electricity
04
M
363/11, 379/64,
H04M 1/74 (2006.01) H04B 3/20 (2006.01) H04L 5/16 (2006.01) H04M 3/02 (2006.01)
Patent
CA 1182935
ABSTRACT A method and apparatus are disclosed which provide a common handshaking protocol for the 201, 202 and 208 modems. This novel handshaking sequence trains up any echo canceller in the circuit, detects the presence of any echo suppressor and uses a conventional signal preamble in the presence of echo cancellers and a sacrificial carrier sequence in the presence of echo suppressors. As in the prior art, a ringing signal is applied to an answer modem in response to a signal from an ori- ginate modem, the answer modem is connected to the communication line after receipt of the ringing signal, and an answerback tone is transmitted from the answer modem to the originate modem after a period of silence following connection of the answer modem to the line. After receipt of the answerback tone, the originate modem is connected to the communication line. In accordance with the invention, this is followed by a period of silence that is sufficiently long to reactivate any echo suppressors in the communication line. Thereafter at least two training sequences are transmitted, one from the originate modem to the answer modem and the other from the answer modem to the origi- nate modem, each training sequence being sufficiently long to train up any echo canceller in the line. The lengths of the training sequences as received are compared with their lengths as transmitted to determine if the length of the sequence was shortened by an echo suppressor. If the length of the training sequences as received are significantly shorter than their lengths as transmitted, a sacrificial carrier is transmitted at the beginning of each transmission of data in a new direc- tion. In the event the training sequences as received are not significantly shorter, each transmission of data in a new direc- tion begins without a sacrificial carrier. As a result, greater data throughput can be achieved in the absence of echo suppres- sors and errors can be avoided while echo cancellers are being trained.
406726
General Datacomm Industries Inc.
Osler Hoskin & Harcourt Llp
LandOfFree
Data transmission over long distance circuits does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data transmission over long distance circuits, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data transmission over long distance circuits will most certainly appreciate the feedback.
Profile ID: LFCA-PAI-O-1227573