CROSS BOX

 A simple box used to introduce crosstalk between phone lines. Cross Boxes
have several uses:

 (1) To eavesdrop on conversations. You are on line #2 listening to your
cheating spouse on line #1 slobbering over the new love.

 (2) To annoy or harass the other line user with whatever crosstalk that's
played into their line.

 (3) As an el cheapo Cheese Box.

 (4) To provide background music, sound effects, etc.

 Many designs are possible. However, the best consists of 600:600 ohm 
transformer coupling between the two lines. Be sure to DC-isolate each 
transformer with a 0.47 uF, 100V non-polarized capacitor between it and the
phone line. A 10K ohm multi-turn pot should be wired in series with one of
the transformer leads to reduce volume as needed. 

 The Cross Box can be used with an audio amp on one side, instead of another
phone line. The audio amp could provide background music, commentary, etc.
It could be used in conjunction with a Crimson Box to provide Music-on-Hold.