This trigger can be tuned to be a fairly sensitive detection algorithm that has rather weak discrimination between noise and seismic signals. As the names imply, carlstatrig performs trigger calculations for one or more stations, while carlsubtrig does the subnet and network trigger logic. Carlsubtrig reads these station trigger messages from the transport ring. Thus there can be more than one carlstatrig or carlsubtrig module running at once.
Provision is made for slow delivery of station trigger messages.
The subnet calculations are performed after a configurable latency period has elapsed. The station trigger algorithm works as follows. In its original form this calculation was done in integer arithmetic. The current calculations are performed in floating-point arithmetic. This obviates the need for some subtle adjustments used in the earlier code, and seems to make the algorithm more sensitive.