Positive or negative edge trigger

 
The analogue trigger input is continuously sampled at the selected sample rate. If the programmed trigger level is crossed by the trigger signal from lower to higher values (rising edge)... Edge trigger. Diagram showing positive edge point in relation to a analogue input signal.
 
...or higher lower value (falling edge), then the trigger event will be detected at the programmed level and the A/D card will start recording.

N.B. Positive and negative triggers can be combined!		 Edge trigger. Diagram showing negative edge point in relation to a analogue input signal.
 
A digital trigger input is also available on the cards faceplate, located alongside the multiple purpose digital (TTL) I/O connections. The edge trigger operation can be used with this input too, however the level is not programmed, instead it works by simply looking for a fast edge. User sets this to be either positive or negative edge recognition, or combined as shown opposite. Edge trigger. Diagrams showing edge points in relation to a digital TTL input signal.

N.B. AND/OR combinations are possible between the analog and digital triggers.

This edge trigger mode corresponds to the commonly used trigger facility found on oscilloscopes.