Browse Prior Art Database

Electronically Switchable Delay Equalizer

IP.com Disclosure Number: IPCOM000074377D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Crouse, WG: AUTHOR [+2]

Abstract

In data transmission systems, it is usually necessary to predistort a transmitted signal or to modify a received signal to compensate for the nonlinear transmission characteristics of the line. Such modifications are introduced into the signal by filters placed in the modulator-demodulator (modem) units which convert the data signals into signals suitable for transmission over a telephone system. Such modems are tested by wrapping the output signal to the input circuit but since there is no transmission line in the circuit, the filter equalizers must be switched out and are not tested.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 2

Electronically Switchable Delay Equalizer

In data transmission systems, it is usually necessary to predistort a transmitted signal or to modify a received signal to compensate for the nonlinear transmission characteristics of the line. Such modifications are introduced into the signal by filters placed in the modulator-demodulator (modem) units which convert the data signals into signals suitable for transmission over a telephone system. Such modems are tested by wrapping the output signal to the input circuit but since there is no transmission line in the circuit, the filter equalizers must be switched out and are not tested.

Shown is a technique for retaining the filter equalizers in the circuit so that they may be tested, but for disabling their frequency responsive circuits so that no signal modification occurs. The drawing shows a number of filter circuits 1 in series between an input 2 and an output 3. The filters are not necessarily of the same characteristics and may be made effective in various combinations to match the characteristics of a transmission line. Each filter may have an operating amplifier 4 having one input connected to the junction of a pair of voltage divider resistors 5 and 6 connected between the filter input and ground. The other amplifier input is connected to the amplifier output by a resistor 7 shunted by a pair of capacitors 8 and 9 in series. Two resistors 10 and 11 are connected at one end to the midpoint of capacitors 8 and 9 wi...