Data communications over telegraph circuits 1917

Anne & Lynn Wheeler

Sometimes the introduction of modern technology leads to a loss of backup capability and failures become more serious.

For instance, when Amtrak inherited the Pennsylvania Railroad's trunk between New York City and Washington, there were signal towers every few miles to control the pbuttage of trains and route them among different tracks as needed. The towers were manned 24-7 and had heavy duty maintenance-intensive relays and signal-communication systems.

Amtrak modernized this was centralized computer control in central locations. This had the advantage of dispatchers being able to see the entire railroad at a glance and required far fewer staff than at individual towers. However, in the event of a system failure, someone had to drive out to the remote location and manually work things; that can add time to recovery. The central computers are more complex and more likely to fail, although they do use redundancy and high-grade fault-tolerant hardware.

As turned out, Amtrak's signal system is quite reliable; I wish the FAA's computers worked as well. (Unfortunately, other parts of Amtrak's NEC infrastructure are 75 years old, like the overhead power lines, and their age is showing.)