Conventions

First of all, the APU references everything from antenna zero’s perspective. Our convention (for AEI only) is to install antenna zero for all tracks on the hut side of the track and the wheel detector on the antenna zero side rail. Most railroads follow this convention. There are exceptions and ways to compensate which I’ll address later. With standard wiring of the original Servo Passive transducers, from antenna zero’s perspective, this makes the left side the “A” segment and the right side the “B” (the manufacturer actually labeled it as “A” and “B” segments). The “A-B” naming was carried forward with the Tiefenbach (SII is the “A”, SI the “B”) and Frauscher wheel detectors (SYS2 is the “A”, SYS1 the “B”).

Car/Tag orientation

Car orientation is determined by which tag is read first. If the site is properly installed/configured, when a train is moving forward, the tags on the right hand side of the train/car will be always be read first (toward the front of the car). If it is the Right coded tag, the car will have “A” orientation. If it is the Left coded tag, the car will have “B” orientation. If it sees the tags on the left hand side of the train/car first, the APU gives a tag orientation error (Tag applied on wrong side or wrong end of equipment). In the DDF report, the “Ti” (tag indicator) field for both tags will show this. For example, forward direction left to right with respect to antenna zero, R0F=Tag programmed Right side, antenna 0, Front of car.

Train Direction

Direction of travel for trains is setup in the Site Information parameter for each active session.

Sessionx.SiteInformation.TrackOrientation=W-E

Referencing from antenna zero, facing the track, enter the Left-to-Right direction (usually railroad direction, may not match the physical direction). Enter for each active session. Note: one railroad may consider the site N-S and a 2^nd may consider it E-W.

Never change this one:

Sessionx.SiteInformation.TrackDirection=L-R

Double Track Interference Location.

At antenna zero, facing its track, are the adjacent track’s antennas to the right or to the left? Enter in following parameter:

Acquisition.ITC1.InterferenceUnitLocation (0=to the right, 1= to the left)

Go to the other track’s antenna zero and repeat for its APU.

Exceptions

Wheel detector mounting

The most common exception is wheel detector mounting. Sometimes it is not possible to mount on the antenna zero side of the track (track joint, switch, routing, other obstruction). If mounted on the opposite rail from antenna zero, the movement of the train will be reversed from expected. There are 2 ways to compensate to maintain conventions. First/best is at installation time-simply reverse the pairs at one point in the wiring-best at the trackside junction box. Now “A” (now SI/SYS1) is still to the left from antenna zero’s point of view.

The 2^nd is to set the wheel orientation parameter.

Acquisition.Operating.WheelSensorOrientation (0=normal, 1=reversed)

Sometimes this parameter is used to correct orientation issues with an existing site. If you are getting tag orientation errors on most of the cars, antenna zero and the A-B transitions are in conflict. Ideally, it should be resolved at the site, but that is not always practical. See the DDF report referenced earlier. Flipping this value will correct the antenna zero and the A-B conflict, but you are basically reversing the entire site logically in the APU. Change the Direction of travel for all active sessions as well. CAUTION: This will also reverse directions for trains already recorded on the APU. Keep in mind for historical purposes:

Sessionx.SiteInformation.TrackOrientation

If change is necessary to correct antenna reversal, it may effect double track logic. We need to know where the interference track’s antennas are located. These settings are based on the antenna 0 location-the antenna physically connected to antenna port 0 of the RF unit.

See Double Track Interference Location above

Antenna 0 location.

Occasionally, it is necessary to place antenna zero away from the hut side. Most common was older video hybrid sites where antenna 0 was placed on the same side of the track as the camera. In double track locations, the camera could not be mounted between the tracks and had to be mounted on the outside. Antenna zero is now mounted on the outside. The wheel detector is still mounted on the antenna zero side of the track, L-R movement still “A” to “B”, maintaining the other site conventions.

Site Maintenance

If parameters were changed, reboot is required (Fast boot OK). Then perform the parameter backup (BP) and update the mirror image (SHELL IBACKUP). Note: Trains will not record while IBACKUP is running. LPMTX version APU102, this takes about 20 minutes (REQUIRES 5.4 Boot ROM). On LX-800 version APU102, it takes about 3 minutes.