Before the Advent of Intercoms, Old Mansions Had a Sash

Multiple Choice

Before the advent of intercoms, old mansions had a sash in each room. Each sash was connected to a bell on a master board in the servants' office. When someone pulled a sash in a particular room, a bell corresponding to the room would ring on the master board, informing a servant where to go to provide assistance.
This system is similar to which of the following?

A) Sparse coding
B) Localization coding
C) Population coding
D) Specificity coding