The jack is not wired incorrectly. You cannot use a 6p4c modular jack universally. The wires in a modular single-line mounting cord are reversed, with respect to the modular ends. The jack in the 625-series (and clones) blocks and the jack in the base of a telephone take this into consideration. Therefore you can't use an "output" jack as an "input" for testing, and expect to get proper polarity.

If you had taken a single-ended modular cord, plugged it into your dial tone source, and fastened its red and green leads to those of the Trimline, you would have gotten the proper polarity at the Trimline.

All of the above is not applicable to 8p8c plugs and jacks, because those are designed to have universal polarity.

I assume that the Trimline is now working correctly?

Arthur P. Bloom
"30 years of faithful service...15 years on hold"