Payphone Recognition Tone
The payphone Recognition Tone ( PRT ), also Kuckuckston or Münzerkennungston ( coin-Kennungston ), is in the telephony one of the A- and B-subscriber audible beep . It is sent by payphones during a telephone connection . The payphone sends out a set tone sequence several times at the beginning of connections.
This is to prevent that publicly accessible telephones such as coin or card telephones cannot be used to make direct billable connections (e.g. collect calls , hand-switched calls) and then nobody pays the call charges. Other devices can also emit a cuckoo tone, for example telephones or telephone systems in restaurants, hotels or hospitals, because the guests or patients should not have collect calls.
Problem
A hand-held operator (operator) can safely recognize from the cuckoo tone emitted by the payphone that there is a publicly accessible telephone set at the other end of the line and will not make the connection in question. However, the automatic collect call exchanges currently used usually do not evaluate the cuckoo tone. It is then not possible to block undesired collect calls.
standardization
The Payphone Recognition Tone is standardized by the International Telecommunication Union (ITU-T). Four different tones are used in Germany:
| PRT | Frequencies [Hz] | Rhythm: tone length [s] - pause length [s] | Cycles |
|---|---|---|---|
| PRT I | 1633-1336 | 0.2 - 0.2 - 0.2 - 2.0 | 5 |
| PRT II | 1366-1024 | 0.2 - 0.2 - 0.2 - 2.2 | 5 |
| PRT III | 1336-1024 | 2.2 - 0.2 - 2.2 - 0.2 | 6th |
| PRT IV | 1645 + 857 - 1215 + 935 | 0.2 - 0.2 - 0.2 - 2.0 | 5 |
- Example for PRT I: 0.2 s 1633 Hz , 0.2 s pause , 0.2 s 1336 Hz , 2.0 s pause ; this sequence of tones five times.
The Payphone Recognition tones used in other countries can be found in the ITU recommendation "ITU-T E-100 series Suppl. 2".
Individual evidence
- ↑ ITU-T E.180 / Q.35 - Technical Characteristics of Tones for the Telephone Service
- ↑ a b ITU-T Supplement 2 (Series E) - Various Tones used in national Networks