Re: Flanger Operation *LINK*

Frank,
The flangers I'm familiar with operated on the Catskill Mountain Branch of the NYC/PC. They looked similar to cabooses, with a cupola for the operator. The cupola was very low, presumably due to low clearances on the NYC mainline. The plow-blade between the rails could be raised or lowered, and the side plow-blades extended or retracted by the operator.
Signs along the right of way, consisting of a metal pole with one, two or three flat metal blades extending at a fixed 45 degree angle instructed the operator what to do.
A single blade meant to retract the side plow on the side the blade pointed towards because of close clearance on that side. A "Y" type configuration atop the pole was an indication to raise the center plow (for switches, crossings, & bridges). Occaisionally there would be a Y with a an additional blade below pointing to one-side or the other. This indicated close clearance & center obstruction (e.g., perhaps a switch adjacent to a platform) (see link).
Hope this helps.
Burr Hubbell