Berger is a startup logging equipment manufacturer from Seattle that appeared to startup around 1950. In their printed materials They used variously the names "Berger Engineering Co., Berger Manufacturing Company, and Smith-Berger Manufacturing Co. They were based in Seattle, and their principal product was making steel towers usually 90 to 100 feet tall which could be moved and stood up on site for highlead logging, effectively replacing the tradition of rigging a 'spar tree' on sight. The towers typically telescoped down by half their length to facilitate transportation.
The towers had their own guy line winches attached to the base of them, usually 6 or 7 of them. the rest of the package included a usually a double drum donkey powered by around 400 hp. In their favorite design the main drum would hold around 2000 feet of 1 1/8" line, and the haulback double that length of a smaller line. Many, but not all of the Bergers were trailer mounted with the tower folding down over the trailer for off highway transport, though for highway transport, the tower needed to be set off the trailer and hauled separate usually on a log truck. As I write this article in 2012, Berger has been gone for quite some time but their machinery is still around and the photos here were taken in the last year.
The secret to satisfactory results in cable logging is and always has been getting sufficient deflection in your yarding line. You need a layout which will permit 10% deflection (line sag) as a function of the distance. This means that if you are out 2000 feet you need 200 feet of line sag. Clearly you don't get that with a 100 foot tower on flat ground, but these things aren't used for flatland logging at least at that distance. The ideal setup is to be able to span a canyon with your line and have the 'tail end' on the next ridge or at least far enough up the side of the next ridge so as to provide the required deflection.
Unlike the more complex 'swing yarders' featured elsewhere on this site, these are typically double drum machines, and if slack pulling is to be used for side yarding a motorized carriage is typically employed.