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Modem Wrap Test Apparatus and Method

IP.com Disclosure Number: IPCOM000082183D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Shropshire, JH: AUTHOR [+2]

Abstract

The "wrap test" for a modem includes a simulator line inserted between the transmitter and receiver portions of the modem. The simulated line is adapted to have a characteristic that is the complement of the equalizer included in the receiver. When the "wrap test" is performed, the equalizer is exercised to better determine the overall performance of the modem.

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Modem Wrap Test Apparatus and Method

The "wrap test" for a modem includes a simulator line inserted between the transmitter and receiver portions of the modem. The simulated line is adapted to have a characteristic that is the complement of the equalizer included in the receiver. When the "wrap test" is performed, the equalizer is exercised to better determine the overall performance of the modem.

Fig. 1 shows a modem 10 including a transmitter 12 and receiver 14. The transmitter 12 includes a modulator 16, line driver 18 and line transformer 20 connected to the simplex line 30 or equivalent. The receiver 14 includes a line transformer 32, preamplifier 34, equalizer 36 and demodulator 38. A simplex line or equivalent 40 is connected to the line transformer 32, and the data out line 42 is connected from the demodulator 38 to a utilization circuit, not shown. The line simulator 44 is connected between the transmitter and the receiver portions of the modem 10.

Fig. 2 shows the line simulator circuit which is adapted to have a characteristic that is the complement of the equalizer 36. The simulator comprises a plurality of amplifiers 46, 46' that are connected in cascade to provide a frequency characteristic, as shown in Fig. 3. By choosing an appropriate number of amplifier circuits 46, the frequency of interest for the modem can be altered to provide the same delay at fH as that at fL. The frequency of interest represents the frequency spectrum of the modem 10 and ...