WHO’S IN CHARGE HERE? - All Aboard: The Complete North American Train Travel Guide - page 108

Dispatchers communicate directly with a train's engineer by
radio. They also control the signals seen by the engineer along the
route. The dispatcher's main and constant concern is knowing
exactly where each train is at all times. To assist the dispatcher,
the engineer checks in by radio regularly—when the train passes
specific checkpoints, when it leaves each station, and at other
times along the way.
There is other, more specific communication between the
train crew and dispatcher, of course. The dispatcher frequently
directs the train to slow down, stop, or resume normal speed. He
may remind the engineer that there are workers on the track at
a certain location or instruct him to reduce speed between two
specific mileposts because that track has recently been laid. When
receiving such instructions, the engineer will acknowledge the call
and carefully repeat the message so the dispatcher will be sure it
was heard correctly. The engineer will often conclude his part of
the transmission by verbally noting the time and the train num-
ber and then identifying himself by name. For important matters,
the dispatcher is also the train's link to the rest of the world. If a
passenger becomes seriously ill, for instance, the engineer can call
the dispatcher and ask her to arrange for paramedics to meet the
train at the next station stop.
Engineer
This is the job we all wanted when we were kids. If you've ever
been one of the privileged few to get a ride in the cab of a loco-
motive, you'll know why. It's quite a thrill to sit up there with all
that horsepower, grandly acknowledging the waves from kids of
all ages as you thunder past. But make no mistake: it's a demand-
ing job, and while it's generally agreed that being a freight engi-
neer is more difficult, the men and women hauling Amtrak trains
around the country are acutely aware that they're responsible for
the lives of several hundred passengers.