Dial test network
Under a Wählprüfnetz is meant a special extension of a telephone network , with which a testing of subscriber lines including the connected phone from a central point is possible.
To measure the subscriber connection line, a test cabinet was connected to the subscriber line at the main distributor (HVT) of the respective exchange in the early days of switching technology . The line to be tested was cut at the main distributor and led to the test cabinet as an internal and external line.
For reasons of rationalization, the fault clearance service of the West German telephone network was largely centralized. For this purpose, a special direct current selector test network with its own switching elements has been set up. Various local networks could then be selected from a test cabinet via the individual options and the subscriber lines could be tested. The construction was carried out by the Deutsche Bundespost in the 1950s. In this context, the central interference suppression points 59 were set up. The dial test network could not be reached by the normal telephone subscriber.
The dial test network made it possible to select all subscriber lines for measurement purposes from test bench 59 via its own dial levels. The telephone connections of unmanned local exchanges (OVSt) could also be checked at any time. (See schematic drawing)
A test group selector was installed in the exchange (see pictures) and a test line selector was installed in each subscriber hundred. The test lead selector was switched on several times so that it was occupied by the group selector as the last line selector. It could be used by the participants as a completely normal line selector. The direct current connection of the two subscriber wires a and b could only be initiated from the test bench via the dial test network
In the superordinate central fault clearance office there was also an exchange test group selector (VSt-PrGW). This group voter was z. B. the test table 59 or the automatic test station upstream. The VSt-PrGW was used to select the desired exchange to which the subscriber to be tested was connected. The participant's line could be measured using the test group selector and the test lead selector.
In the case of dial-up test networks, a basic distinction must be made between networks with galvanically connected lines and those with sealed lines. In the dial test networks, depending on the number of OVSt or the size of the local networks (ON), exchange test group selectors (VStPrGW), continuity test group selectors (DgPrGW), test group selectors (PrGw) and a test line selectors (PrLW) in each participant hundred were used as voters.
The test benches 59 were connected to the test network with galvanically connected lines via a direct current test transmission (GPrUe). When setting up the network, the aim was to control the connections to be tested as accurately as possible.
In dial-up test networks with galvanically sealed lines, a remote-controlled test station (FPrPl) is also used. This FPrPl corresponds in its measurement functions to the test bench 59. It is controlled from the test bench of the central interference suppression point by number switch pulses, it converts the measured direct current values into alternating voltages in frequencies of the voice band and sends them back to the central point. These frequencies could be transmitted over any line. In the control center, alternating voltages were converted back into direct current values. A remote test transmission (FprUe) is switched on between the test bench and the dial test network instead of the GPrUe. The connection transmissions (AnUe) also belong to the dial test network. The lines that cannot be controlled via PrLW are manually connected to the test network via this AnUe. These are primarily unidirectional direct dialing lines and connection lines to private branch exchanges.
The automatic test station (APrPl) was created to streamline the routine tests that the suppressor would have to carry out after completing his repair work. The APrPI was equipped with measuring circuits. These only carried out the limit value controls and gave the suppressor and a good / bad statement. The APrPI was dialed by the suppressor under a specific call number. Then, by dialing the connection number of the connection to be tested, a connection was established from the APrPI to the connection via the dial test network. After hanging up the handset, the APrPI measured. The APrPI calls the connection to display the measurement result. After picking up the handset, the suppressor receives the result of the measurements through certain audible tones.
Web links
- Dial test network (accessed on July 10, 2017)
- technical description