1) Telephony equipment
Found on
https://www.crosswordclues.com/clue/calculagraph
The Calculagraph is a device which mechanically calculates and prints the elapsed time between two events. Their best known, earliest use was as a means of tracking of table usage in pool halls. Later, until the advent of the digital era, they became the standard way to clock the duration of toll telephone calls. == Invention == Henry Abbott, a wa...
Found on
http://en.wikipedia.org/wiki/Calculagraph
No exact match found.
