Inverse engineering

Introduction

In this section I present two modem schematics:

SoftV92 Data Fax Modem

This diagram shows how an internal SoftV92 Data Fax Modem interacts with phone line. The modem is from Zoltrix but a Conexant utility says it is a "Churchill Data Modem". This schematic may be useful to fix a similar modem.

Schematic

Integrated circuit

IC# signals run to the indicated IC pin number, a 100 pin SMD chip with the following inscriptions:

CONEXANT
HSFi
CX11252-11
E151518.1
0136	MEXICO

SoftV90 Data Fax Modem Speakerphone

The following schematic belongs to another PCI internal modem:

Schematic

First part shows phone line interface and second part microphone/heads jacks.

Phone line interface

3.3V supply is from a 3 leg SMD regulador running from 5V. The capacitor labeled "270V" parallel to the "LINE" input is a varistor of that value.

Audio interface

Integrated circuit

The IC in this modem has the following inscriptions:

RS56/SP-PCI
R6793-11
(C) ROCKWELL 98
9919  879026.4
KOREA

Notes

I cannot measure SMD capacitors and inductors so they are unmarked on the schematics.

These schematics have been drawn tracing the circuits and may contain errors. I am not responsible for their use.

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