The contribution deals with the application of new pig signalling techniques on the basis of ultrasonic probes and methods. It will be shown, that ultrasonic techniques are extremely versatile in order to work under different operational conditions and can be adapted to very different situations. Especially, the possibilities are explainded and exemplified which arise for pigging campaigns at gas pipelines. Two principal approaches will be discussed and combined. First, ultrasound can be sent actively into materials. It can be influcend by changes of the system. This information can be read out by the received ultrasonic pulses. Second, many technical systems, such as pipelines and moving pigs, produce a lot of valuable noise which can be exploited for pig signalling.