For what it's worth, a picture of Abajo: the end of CTC and the beginning of double track. With a neighborhood and a menacing fence bordering the east side, and the Albuquerque yard on the west side, Abajo is extremely difficult to access; hence the poor picture angle. The view above looks north, with the city's skyline just visible by the Abajo sign. The Albuqurque area was part of a 1917 improvement project to expedite the flow of passenger, freight, and local traffic through the metropolitan area. In addition to 4 miles of double track from Abajo through Albuquerque to Hahn, two interlocking plants at each end were constructed. The 4 miles of double track was initially signaled with eleven, 3-position upper-quadrant Style-S's. Their motors were D.C. and the system used non-polarized line for control.

Abajo had a 5-lever mechanical interlocking that featured approach, indication and section locking. Though no layout of the old plant exists, 5 levers would most likely handle no more than two switches and their protective signals. So why install an expensive manned-interlocking when a spring-switch lined for one direction would work as well? In 1917 spring switches were uncommon and railroads viewed them with a certain amount of distrust, not believeing a spring switch could reliably return to its original position. Another reason might have been flexibility, where the tower could route a passenger or freight against the current of traffic in order to avoid a local switcher working the many industries. In any event, the AT&SF elected to install a power switch rather than a spring switch when the plant was converted to CTC in 1959. In a typical minimalist philosophy of the AT&SF, the facing head block signal is devoid of a lower "B" unit. In such an installation a switch lined against the current of traffic would most likely give a flashing red. The signal also lacks a number plate, which marks it as an absolute signal. As you will see later, absolute signals can be controlled signals or automatic signals.

Nor are any pictures of the Abajo interlocking known to exist. However, the eastward signal is in all likelihood an original except for the searchlight. This is not a typical Raton Line installation. The case is from a Style-S and it is mounted parallel to the track. The AT&SF preferred to mount their cases perpendicular to the tracks in the believe that it afforded more protection from passing trains while the signalman worked within the case. This seems counterintuitive, and virtually no other railroad adopted this policy. Also note the heavier T-2 bell casting, which would leave one to believe that a T-2 once grace the top of the mast.