Digital pattern generators can produce either repetitive, or single-shot signals in which case some kind of triggering source is required (internal or external).
PC-based digital pattern generators are connected to a PC through peripheral ports such as PCI, USB, and/or Ethernet (see, for example, the "Wave Generator Xpress" from Byte Paradigm, connected through USB).
They use the PC as a user interface for defining and storing the digital patterns to be sent.
Most digital pattern generator add features such as the ability to generate a repetitive sequence or a digital clock signal at a specified frequency, the ability to use an external clock input and triggering options, to start pattern generation upon the reception of an event from an external input.
In safety-critical technology such as automotive, specialized electronic systems are involved in keeping its correct functioning.