A wire signal is a brevity code used by telegraphers to save time and cost when sending long messages.
In the above list, the numbers 19 and 31 refer to train order operations whereby messages from the dispatcher about changes in railroad routing and scheduling were written on paper forms.
Today, amateur radio operators still use codes 73 and 88 regularly, and -30- is used in journalism, as it was shorthand for "No more - the end".
The Young Ladies Radio League uses code 33 to mean "love sealed with friendship and mutual respect between one YL [young lady] and another YL"[3] or simply "hugs."
[1] The following code was taken from 1873 telegraph rulebook of the Lakeshore and Tuscarawas Valley Railway Company of Cleveland, Ohio.