Figure 1 - Phone Line Simulator Wiring Diagram   
          
          150 Ohm Resistor
    *---------/\/\/\/---------*     * => twist wires together & cover
    |                         |          with tape
    |                         |
    |                         | Modular             Modular
    | red wire                | Telephone Jack      Duplex
    |                     x x | x x x x x x x x x   Jack     Phone Cord to
    | +                   x   |    green        x   o o o o  Fax Machine
  -----                   x   |    wire         x   o     o ============>
   ---   9V Battery &     x   ----------- x x x x o o     o
  -----  Snap Connector   x               x     x         o
   ---                    x   ----------- x x x x o o     o
    | -                   x   |    red    | |   x   o     o ============>
    |                     x   |    wire   | |   x   o o o o  Phone Cord to
    | black wire          x x | x x x x x | | x x            Computer
    |                         |           | |                Fax/modem
    |                         |     black | | yellow
    |                         |     wire  | | wire
    |                         |         not used
    --------------------------*