**ShowPlay Reference Manual, Chapter 3 (ControlVariables): atrig_val**
===== Atrig_val -- External signal level to use as triggering threshold  =====
The ATRIG_VAL variable is used to specify how to use an external analog signal to trigger the start of a paradigm. 
ATRIG_VAL is used when TRIG_FLAG is set and [[jvs:cigal:showplay:manual:chapter3:trigtype|TRIGTYPE]] is 3, indicating that an external analog signal will be used for the trigger. 
The [[jvs:cigal:showplay:manual:chapter3:atrig_chan|ATRIG_CHAN]] variable should be set to specify which analog channel is to be used as the trigger signal.

Analog voltage transitions that cross the ATRIG_VAL threshold will be considered trigger pulses. By default, either positive or negative transitions are recognized as triggers for starting the paradigm (TRIG_FLAG & 2).  If TRIG_FLAG indicates that trigger pulses should be recorded throughout the paradigm, only positive transitions will be recorded.

**See Also:**\\
[[jvs:cigal:showplay:manual:chapter3:trigtype|Trigtype]],
[[jvs:cigal:showplay:manual:chapter3:atrig_chan|Atrig_chan]],
[[jvs:cigal:showplay:manual:chapter3:atrig_val|Atrig_val]],
[[jvs:cigal:showplay:manual:chapter3:dstartmask|Dstartmask]])\\
[[jvs:cigal|CIGAL Home]], 
[[jvs:cigal:manual|CIGAL Manual]], 
[[jvs:cigal:showplay|ShowPlay Home]], 
[[jvs:cigal:showplay:manual|ShowPlay Manual]], 
[[jvs:cigal:showplay:manual:chapter3|InputParameters List]], 
[[jvs:cigal:showplay:manual:help|Manual Help]]