Which of the following is used to create an electronic signal that can be sent to the central nurse call equipment?

A headend module is the central processing and control unit of the nurse call system that receives and routes signals, not the device that originates them.

An initiation device, such as a patient call button or pull cord, is specifically designed to generate the electronic signal that triggers the nurse call system - it is the originating component that a patient interacts with to request assistance, and its signal is transmitted to the central nurse call headend for processing and routing.

A notification device is an output component such as a corridor light or dome light that displays or sounds an alert after the signal has already been processed by the system.

A two-tone device is an audible notification output component used to signal staff with distinct tones, not a device for creating the initial patient call signal.