The actual workings of what happens at a pahse gap can be explained simply.
There are 6 pahse gaps on electrified lines where I am qualified, two of which involve a voltage change. On the other 4, I have been told that the phase gaps allow for different suppliers of electricity on either side. There are also 3 on the Coast Line, I of which involves a voltage change. They are:
Meadows (Between Meadows interlocking and Kearny Jct)
Kearny Jct (On tracks 5&6, with a voltage change from 25Kv on the M&E to 11Kv on Amtrak)
Cape (On the singe track Waterfront Connection, with a voltage change like that at Kearny Jct.)
Maplewood (Behind the Pathmark in Maplewood, and right by the detector)
Morristown (About a mile west of Morristown station)
Sterling (MP 29, just west of Sterling station)
Aberdeen (Just west of Matawan station, this also has a voltage change from 11Kv east of to 25Kv west of. Additionally, power east of there is provided from Amtrak as the catenary is connected at Union)
Laurel (West of Hazlet, near the Laurel Ave undergrade bridge)
Red Bank (Just west of Red Bank station)
Anyone qualified on the physical characteristics of the railroad will know exactly where these are located, however, they are also marked by two signs on the catenary poles, or in the catenary itself. One cat pole from the actual dead section of the phase gap, which is about 10 feet long, there is a PG sign, which is an indicates an approaching phase gap. At the actual dead section, there is a phase gap marker, which is a white triangle, with a black dot in the center of it. This is where if you are operating an MU train you must have the controller back to off.
Now, lets say I am operating an ALP-44, or 46 east towards the phase gap at Kearny Jct. As I approach the phase gap, I will back off the throttle so that once I reach the PG signs, I have the throttle back to "O", which is the same as idle on a diesel. Located between the rails, usually near the PG signs, but sometimes a little farther back, are two yellow magnets. There are two magnets just in case one gets stolen, knocked out of position, or for some reason fails to do its job. The magnets are detected by an "antenna" (their term, not mine) located underneath the locomotive which causes the main circut breaker (MCB) to open or close, depending on its current position. Whatever position it is in now, it will do the oppisite, if possible. This has the same effect as the pan being dropped. This is also why the lights go out on the train when passing through a phase gap. Once the locomotive clears the dead section, once again, a set of magnets will be encountered. Before the MCB closes, the locomotive will check the line voltage, and make sure the transformer is set up to operate under that voltage, changing the transformer setup if required. Once that is done, the locomotive will power up, the engineer may bump for power, that is, open the throttle rapdily to get a bump, to make sure the locomotive is come totally back. Sometimes, you will not get traction power after passing through a phase gap, although you will get the HEP back, this allows you to make sure. Bumping for power is only done on the cab car as the locomotive has an amp meter to show if the traction motors are taking power, and the cab car does not.
Now on MU's, they do not open the MCB prior to a phase gap, and so an engineer must have the controller back to off so as not to draw an arc across the dead section of the phase gap, which would blow the line behind the train. When the pan of the MU gets to the dead section of wire, the equipment automatically switches to dynamic brake to supply power to keep the lights lit, and the rest of the systems operating. In the even that the line goes dead, they will do the same thing, until the train stops.
In an ALP it is not required to shut off the throttle, as the magnets will open the MCB anyway, although this would make for a very rough ride, and could damage the electronics on the ALP.
Finally, as to why the cat poles just on either side of a phase gap on the coast line are painted lime green, there is a simple answer. When the E60's were running, it was necesscary to manually open the MCB at phase gaps. To remind engineers of this, the cat poles just before the phase gaps, as well as the button on the control stand were painted lime green.
Proven Theory #2 - If you don't work for the railroad, you don't know more than the people who do, no matter how many years you've hung around the tracks, or how well you think you understand railroading.
Rest in peace Jtgshu.