a unit with sound will start at a slightly higher voltage than a unit without sound

This is a Bowser 42064 HO Scale Pennsylvania H22a Circle Keystone Clamshell Hopper Car #410401

Here is a USA Trains R31097 Southern Pacific Daylight Ltd

Dinensions: 4" x 2½" x 3"

Bachmann 65201 HO Pennsylvania GG-1 Electric Locomotive Standard DC #4912 ProductID_11475920 a unit with sound willThis is a Bachmann 65201 HO PRR Brunswick Green Single Stripe #4912 DCC Ready. The GG1, one of the PRR's most famous and recognizable locomotives, is also one of the most curiously designed. Technically two locomotives under one shell (a G class locomotive is a 4 6 0 by PRR specification, therefore the GG1 was two G locomotives in a 4 6 0: 0 6 4 arrangement). This added up to a 4. 6k horsepower locomotive that was staggeringly powerful, even by