Browse Prior Art Database

Variable Speed Modem Tailing

IP.com Disclosure Number: IPCOM000039120D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Fieschi, J: AUTHOR [+3]

Abstract

Modem networks are sometimes made to include modems provided with a back-up operating speed, which is not necessarily a submultiple of the nominal operating speed. Any modem tailed to the modem susceptible of switching to back-up speed, should adjust itself to this speed and receive a Transmit clock signal which is not at its own nominal frequency. The tailed modem may be used at its nominal speed. Assume, for instance, that a base band modem operating at 14400 Bps is tailed to a modem operating at 12000 Bps. Then one may derive a sub-channel at 12 KBps by using 5 bits over 6 and by marking the sixth bit, for instance, by forcing it to zero.

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Variable Speed Modem Tailing

Modem networks are sometimes made to include modems provided with a back-up operating speed, which is not necessarily a submultiple of the nominal operating speed. Any modem tailed to the modem susceptible of switching to back-up speed, should adjust itself to this speed and receive a Transmit clock signal which is not at its own nominal frequency. The tailed modem may be used at its nominal speed. Assume, for instance, that a base band modem operating at 14400 Bps is tailed to a modem operating at 12000 Bps. Then one may derive a sub-channel at 12 KBps by using 5 bits over 6 and by marking the sixth bit, for instance, by forcing it to zero. In the transmitting section of the network (see figure), the data are fed into a zero insert device (B) inserting one zero every 5 bits under the control of a clock device (A) providing clock signals at 12000 and 14000 Bps. In the receiving side, a phase-locked oscillator (c) is made to monitor the received data in, destuff the data train, and provide the original data train as an output to the Data Terminal Equipment (DTE).

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