# Fixed, immediate, and follow switches
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In MediaLive, you can categorize input switches according to the start types for the switch. 
+ Fixed – A fixed input switch starts at a specific time.

  Fixed switches use UTC time. They don't use the timecode of the input. 
+ Immediate – An immediate input switch starts as soon as possible. This type of switch is more like a fixed switch than a follow switch because it interrupts the current input. The advantage of this switch over a fixed switch is that you don't have to calculate any buffer in the start time.
+ Follow – A follow input switch starts when the previous input has ended (when MediaLive has reached the end of the file).

This start type is a property of the switch, not a property of the input itself. Therefore, in the schedule you can switch to a specific input with a fixed switch, and then later switch to the same input with a follow switch.

## Types of switches and types of inputs
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The combination of types of switches and types of inputs (file and live) means that there are these types of switches:
+ A file input with a fixed start. The previous input can be a file or live input. At the specified start time, MediaLive stops ingesting the previous input and switches to the new input.
+ A file input with an immediate start. The previous input can be a file or a live input. As soon as possible after you enter this switch in the schedule, MediaLive stops ingesting the previous input and switches to the new input. 
+ A file input that follows the previous input. The previous input must be a file input. It can't be a live input because a live input doesn't have an end, so the switch would never occur. 
+ A live input with a fixed start. The previous input can be a file or live input. At the specified start time, MediaLive stops ingesting the previous input and switches to the new input.
+ A live input with an immediate start. The previous input can be a file or a live input. As soon as possible after you enter this switch in the schedule, MediaLive stops ingesting the previous input and switches to the new input. 
+ A live input that follows the previous input. The previous input must be a file input. It can't be a live input because a live input doesn't have an end, so the switch would never occur. 

The following table summarizes the inputs and start types.


| Current Input | Next Input | Possible Start Type | 
| --- | --- | --- | 
| File | File | Fixed or Immediate | 
| File | File | Follow | 
| File | Live | Fixed or Immediate | 
| File | Live | Follow | 
| Live | File | Fixed or Immediate | 
| Live | Live | Fixed or Immediate | 

## Follow chains
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A series of follow input switches is called a *follow chain*. When each input ends, MediaLive automatically starts ingesting the next input. Here is a diagram of a follow chain:

```
   Input A    Fixed or Immediate   File
     Input B  Follow               File
     Input C  Follow               File
     Input D  Follow               File or Live
   Input E    Fixed or Immediate   File or Live
```

The follow chain starts with the *reference action*—the input above the first follow. It ends with the last follow input. In the preceding example, the chain starts with the reference action input A and ends with input D. Inputs A, B, and C must be files because they must have a defined ending so that the next input can successfully follow. Input E breaks the chain because it is fixed or immediate.