...is not the title of any electronic music album, but a keyword to describe this fellow:

Deutsche Bahn has two class 719 ultrasonic permanent way inspection trains in its inventory. This here is 719 001 (with the "B" car in front, which is numbered 719 501) which was delivered in 1975. This set is based on the class 614 regional DMUs, of which 42 sets were built between 1972 and 1975. The other set, 719 101, is a much different design by Plasser & Theurer which was built in 1996.

719 001 has a maximum travelling speed of 140 kph and a maximum measuring speed of 50 kph, with two diesel-hydraulic power packs located in the end cars providing 448 kW each. The "A" car, 719 001, contains a galley, dining room, lavatory with shower and three sleeping bunks, while the "B" car has another five bunks and a lavatory. The measuring equipment, including the vertically suspended ultrasonic sensor frame below the floor, is located in the intermediate trailer, designated 720 001.

And a trailing shot of the "A" car. Note the inspection pantograph on the roof, which is complemented by a TV camera which you may be able to spot roughly in the middle of the roof.

This image shows a variety of electric and drinking water replenishment sockets, as well as the braking gear, which is a standardized Knorr brake (KE) with setting "R" only, automatic load-dependent brake force adjustment (A) and disk brakes (encircled D).

This is another bunch of technical inscriptions which reveals a few additional details. Each of the three cars has one of these plaques. The unit is described as a "schweres Nebenfahrzeug" which is a generic term for departmental stock with no other use aside from these departmental tasks - and as an ultrasonic rail inspection unit. Car 719 501 alone is indicated to have a weight of 47 tonnes and payload of one tonne, as well as a braking weight of 74 tonnes. Ten persons are permitted on board, and the top speed is given as 140 kph. Its last revision was completed at the Cottbus repair works (BCSX) on 16 September this year, with the next major revision being due until 16 September 2016.

Additionally, the unit is not allowed to be humped or to enter shunting facilities, can only be towed at the end of a train and must be treated as an "außergewöhnliche Sendung" when being transferred dead in tow - meaning it is considered a kind of "exceptional load" in this event. I could imagine this to have to do with either the ultrasonic sensor frame or the unit having only the "R" brake setting available.