If you don't plan to go to DCC and want to control the sounds in a QSI-equipped sound loco (Broadway Limited, Atlas, and P2K), you pretty much need it. You can sort of operate the horn and bell by flippign the direction switch rapidly, but the Quantum Engineer gives you much more convenient control, plus allows you to adjust volumes and other goodies. The one sold by Broadway is exactly the same as the one sold by Atlas and Walthers (Life-Like).
--Randy
Modeling the Reading Railroad in the 1950's
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