In contrast to the IT, the PT has extended options for requesting information. The inputs are referred to as message points. These can be parallel or serial inputs. The message points are divided into the following sections depending on their position in the access route:
- Advance log-in with the Advance or Block sub-functions
- Main calling detector
- Auxiliary check-in
- Check-out
When a request is made at a message point, a time counter is started, the so-called detector waiting time. The detector waiting time contains the time since the request at a specific message point. At the same time as the request is made at the first message point, a time counter is also started for the relevant traffic stream, the so-called traffic stream waiting time. The traffic stream waiting time contains the time since the request, corrected if necessary, by the calibration value of the traffic stream. This means that a PT is considered to have been requested. There may be several PT vehicles on such a request route. These are managed in vs | plus according to their order of request.