> For the complete documentation index, see [llms.txt](https://emotiv.gitbook.io/extender-manual/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://emotiv.gitbook.io/extender-manual/hardware_triggering.md).

# Hardware Triggering

The Extender’s hardware triggering feature allows you to mark external events for post-processing. The input trigger pulses are injected into to the headset data stream within +/-1 sample. There is a fixed 60ms delay between the trigger and the channel signal data which is due to the filter delay for the channels.The trigger pulse is shown in EmotiVPRO as a pink line and is also saved in the hardware column when exporting a file.

![EmotivPRO Trigger Pulses](https://lh3.googleusercontent.com/eCigpkNQny4wYK9QpohujPl_BiYyXg4AWVk8UhuZ-PiWYzPvksNkwfcHY2UaDzduOpsgR0S8WvOXM99-e-UgsvhOoef5ZSvdVDkLADFi3ROqADjQUEp5fc455bF6T3WzqlWNNwcW)

EMOTIV has provided a custom 1m trigger cable with every extender. The cable has two tinned wires red and black that can be connected to an external trigger source. The input polarity of the trigger is reversable and utilises an opto-coupled photo transistor Vishay VOL628A (see [datasheet](https://www.vishay.com/docs/82401/vol628a.pdf)). This component requires a minimum of 1mA forward current and maximum of 60mA. The input design has has an internal limiting resistor of 1kOhm. The trigger input voltage need to be between 2.5 -15V and can be driven directly from an arduino or a parallel port. Please see below Arduino examples:


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