The original fire alarm control panels did not have a method for people to control the fire alarm systems, like a silence button feature or a reset button feature. If someone activated a pull station, the fire alarm system would "Turn On" and sound the alarm. In order to silence or reset the system, the pull station had to be reset.
There were two lights on many of these panels. One light would show that there was power to the panel, and the other light often just turned on if there was trouble with the system wiring. When the building's horns were sounding off, people figured out that the fire alarm system was in alarm. If there was trouble with the system, a buzzer inside the panel, close to the panel, or remotely located by an office or building entry sounded off. In essence, the remotely located buzzer would "repeat" the local buzzer.
Zone Lights and Passive Remote Panels
As systems got larger, each firefighting zone in the building that was covered by the fire alarm system had its own red light on the panel. When a red alarm light turned on, the firefighters would know where to look for a fire.
But there was a problem. In those days, the fire alarm control panel was usually located in an electrical room in the basement. To solve that problem, a remote panel with the same zone lights would be located at the entry for the firefighters, or even in an office somewhere. These panels were passive, there were no buttons to control anything. The remote panel with lights would "repeat" the lights shown on the panel.
Control Buttons and Active Remote Panels
Once a fire alarm system is in alarm, an improvement to the system was the ability of the control panel to stay in alarm; once the alarm system was in alarm, it would latch, or stay in alarm. Then there were buttons added to the system to "Silence the Alarms", "Reset the Alarm System", and "Silence the Trouble Buzzer".
These buttons were added to the control panels. The buttons were also added to some of the remote panels to allow the remote panels to actively control the fire alarm system. The remotely located buttons would be "repeated" at the control panel. Of course, the control buttons on the remote control panels could only silence or reset the system if someone in authority was pressing them, so key switches were included, or passwords were necessary.
LCD Readout is a Fancy Light Panel
When computer style Central Processing Units (CPUs) were added to the control panels, fancy displays showing which zone was in alarm, and other status information was displayed. The remotely located LCD displays would "repeat" what could be seen on the LCD display at the control panel.
An Annunciator is a Remote Panel
The word Annunciator and the words Repeater Panel are almost completely interchangeable. Some people use the words Repeater Panel because that describes the location. Some people use the word Annunciator because the exact same panel can be on the fire alarm control panel itself for the "Annunciation and Control" as the repeater panel used in the remote location for "Annunciation and Control".
Passive, Active, LCD Display, and Annunciator
A "Repeater" panel is used in a remote location, away from the control panel. It passively displays the condition of the fire alarm panel. If there are control buttons on the Repeater panel, it can also actively control the fire alarm system. A LCD display is an expanded version of the Repeater panel.
A Repeater panel, whether it is just a light panel, also has buttons, and even has an LCD Display is an annunciator.