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Flyer Track Trips
Flyer 670 pressure trip compared with 697 electromagnetic trip trips 

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(From the S-Trains mailing list)
   697: pressure trip. Weight of passing train opens one contact, closes
   another. Adjustable so loco only or any car sets it off, since locos are
   heavier. Contacts may become bent ; try to straighten. Conatct points may
   become dirty; clean with #600 sandpaper. Main problem: can go out of
   adjustment and send power to solenoids when it isn't wanted or for too
   long, burning out solenoid if for example a train is stopped over the trip,
   or trip gets stuck. i use them a lot but they have to be watched all the
   time. When used with rubber roadbed, cardboard must be placed under disc
   to compensate for roadbed raising track approx. 1/16".

   670: electromagnetic trip: power to an isolated rail section goes through
   a coil which pulls contact closed when a loco is receiving power in the
   isolated zone. Contact opens when track power is cut off. Some 670's are
   adjustable to a degree w an adjustment screw; some are not. Problems: 1.
   Not all that sensitive and accurate, often slow acting. Performance
   depends to some extent on amount of track power at any given time (i.e. how
   fast train is running). 2. causes power drop since the coil uses some of
   the track power. Locos will slow or stall in the isolated zone, especially
   2 motor diesels. Generally not good for use in reverse loops where
   polarity is reversed by a track switch. Good in an area where you may want
   to stop a train, since contact will open then and not burn out an
   accessory.

   Lockout eliminator: has nothing to do per se with track trips. Used with
   train stopping accessories, esp the 761 semaphore. An isolated zone is
   created to stop a train; with the semaphore, in the base post rail.
   Lockout eliminator allows a trickle of electricity into this zone so the
   reverse unit does not cycle. Sam the Sem, talking station have them built
   in. New locos from LTI and AM will often creep in such a situation because
   they use much less power than classic Flyer.

   Hope this helps.

   Tom Jarcho