Ringback number

The Postprüfplatz ( PPrPl ) was used in analog local exchanges for quality assurance of subscriber lines and terminating equipment (especially telephones ). The installer called after finishing his work the technician on the operating space of PPrPl in order to obtain confirmation from him the correct functioning of the system.

Tasks

• Determination of line impedance and loop resistance
• Insulation resistance at hook
• Pulse timing of the switch number
• Function of the bell

Automation

During the 1960's the PPrPl by the unmanned automatic Postprüfplatz ( APPrPl ) has been replaced, the installer forwarded to the results of each test automatically by audible tones. Due to the risk of abuse of the bell function test, the selection numbers of APPrPl were confidential, different from exchange to exchange and were changed frequently.

• Switching technology
• Testing