This two-state characteristic of switched circuits is what links electricity to logic, for each relay-controlled circuit can be seen as a truth table, where current flows from the output only when specified input conditions are satisfied, and logical operations can be seen as physical devices that emit an output pulse if and only if all of their input switches are on, or off, or some specified combination, In the 1930s, telephone systems were using ever larger and more complicated mazes of circuits controlled by these relays.
(only when specified input conditions; are; satisfied) (telephone systems; were using; ever larger and more complicated mazes of circuits; T:In the 1930s) (logical operations; can be seen; as physical devices) (physical devices; emit; an output pulse if) (current; flows; from the output) (circuits; controlled; by these relays)
only when specified input conditions telephone systems logical operations physical devices current circuits
are were using can be seen emit flows controlled
satisfied
ever larger and more complicated mazes of circuits T:In the 1930s
as physical devices
an output pulse if
from the output
by these relays