# How SCTE 35 actions work
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You can set up an action to insert a SCTE 35 message in the channel. There are three types of actions:
+ Action to insert a splice\$1insert into the channel: a SCTE 35 message with splice\$1command\$1type set to splice\$1insert.
+ Action to insert a time\$1signal into the channel: a SCTE 35 message with splice\$1command\$1type set to time\$1signal.
+ Action to insert a SCTE 35 return-to-network message into the schedule in order to end a splice\$1insert that either has a duration or has no duration.

Before you add SCTE 35 actions to the schedule, read [Processing SCTE 35 messages](scte-35-message-processing.md).

**Insert SCTE 35 message with fixed start**  
When you create the action, you include a start time. The start time for the action must be at least 15 seconds in the future but not more than 14 days in the future. After that cutoff, MediaLive rejects the request to create the action. 

After you have created the action, the action sits in the schedule. Approximately 15 seconds before the start time, the schedule passes the action to the channel. At the start time, the channel inserts the SCTE 35 message into the stream.

After the channel inserts the message, MediaLive processes the inserted message in the same way as it processes messages that were already in the source content. 

**Insert SCTE 35 message with immediate start**  
When you create the action, you set the start type to *immediate*. 

The schedule immediately passes the action to the channel. The channel immediately inserts the SCTE 35 message into the stream.

After the channel inserts the message, MediaLive processes the inserted message in the same way as it processes messages that were already in the source content. 

**Insert SCTE 35 message with follow start**  
When you create the action, you specify the input switch action that you want this action to follow. That *reference action* must be an input switch.

The input for the reference action must have a source end behavior of *Continue*. To find the **Source end behavior** field, go to the **Create channel** page, find the input in the **Input attachment** list, and then find **General input settings**. 

After you create the action, the action waits in the schedule. Just before the reference action is due to finish, the schedule passes the action to the channel. As soon as the current input has finished, the channel inserts the SCTE 35 message into the stream.

After the channel inserts the message, MediaLive processes the inserted message in the same way as it processes messages that were already in the source content.