Who doesn’t know what a trigger is? This is one of the very first devices that a ham radio encounters after familiarizing itself with the basic elements of electronics, such as resistors, capacitors, transistors.
So what is a trigger?
By definition, it is an element with two stable states. Its simplest non-electronics example is a switch. It also has two stable states - on (on) and off (off). For a trigger, these states will sound accordingly - in a single state (on) or reset (off). In a single state, the output of the trigger contains a voltage slightly less than the supply voltage, in the reset state - a low voltage level. This is where its name comes from, i.e. the element is in one position. Translated from English, the trigger is a latch.
The simplest will be an electronic trigger on transistors. For its manufacture, two transistors, several capacitors and resistors are required. The first use of a trigger will be to use it as a switch.
Often you have to perform a simple action - press the button and then release it. So, usually this action is remembered by a trigger. When a button is pressed, it is set to a single state, and then the device already understands that it needs to work in the mode specified by the pressed button. To exit this mode, press another button, then the trigger will reset and a new operation mode will be set.
However, all of the above is not a complete answer to the question of what a trigger is. This is only one of the possibilities of its use.
There is a wide variety of trigger implementation schemes; there is even a special class of integrated circuits, which are also elements with stable states.
Implemented a variety of types of triggers that differ in circuitry and control principles.
It is enough just to mention such elements as D-, RS-, JK-trigger, synchronous, asynchronous, single-stage, two-stage, counting triggers. All of these options are elements of digital devices. They are used in a variety of tasks, from remembering the state of a button (pressed or not) to participating in signal processing.
Therefore, to the question of what a trigger is, you can get completely different answers:
is an element of memory of digital devices, an elementary cell of memory;
is a logical element involved in the processing of a digital signal;
is a basic element of digital circuitry.
However, even all that is already listed does not cover the possibilities of using a trigger. So, it can be implemented on electromechanical relays or on power elements. You can use a trigger to control power elements.
Finds application not only the idea of an electronic device on transistors, but also the idea of using the latch principle, the principle of performing some action when a certain event occurs. This is especially often used in programming. And in many other cases, a similar method is implemented. This is a very convenient principle when a subsequent event occurs after the implementation of the given conditions.
Therefore, an unambiguous answer to the question of what a trigger is is hardly possible to get. Here you should definitely clarify what is meant by this word.
If this is an electronic product or an element of digital circuitry, then the answer will be one.
If the word “trigger” refers to the principle of application regarding the use of the concept of a latch, fixing the occurrence of an event, then the areas where this principle can be implemented can be very different, from programming to other areas of human activity.