Telephony Training System (8086)

The cornerstone of the TTS is the Reconfigurable Training Module, Model 9431.

This module, which uses state-of-the-art digital signal processor (DSP) technology, can be programmed to act as different parts of a telephone network, such as a digital central office (CO) of the public switched telephone network (PSTN) or a digital PABX.

Analog and digital interface cards, which the students install in the training module, allow connection of real analog and digital telephone sets and trunk lines.

For example, a central office can be easily implemented by inserting an analog line interface card into a training module programmed to act as a central office. Similarly, a simple telephone network can be set up by inserting analog line and digital trunk interface cards into two training modules programmed to act as central offices, and by interconnecting the two modules via a trunk line.

A Pentium-type host computer is connected to the training module through a high-speed data link (Ethernet link with TCP/IP protocol). The host computer is used to configure the training module as a digital CO or a digital PABX, using the included Lab-Volt Telephony Training System (LVTTS) software. This Windows™-based software has an intuitive user interface that displays the functional block diagram of the telephony equipment (line interface, central office, digital PABX, etc.) implemented in the training module.

The LVTTS software allows students to perform step-by-step observation of call routing sequences, and to observe real signals throughout the system in both the time and frequency domains using virtual equipment.

A powerful data-logging instrument in the LVTTS software allows recording of all ISDN layer-3 messages that are exchanged between ISDN entities (call processor in a CO or PABX, digital telephone sets) during telephone calls. This enables students to achieve thorough investigation of the ISDN signaling protocol.

The LVTTS software also allows various system parameters, such as the companding type, the number of voice channels, the telephone ringing cadence, and the call progress tone frequencies and modulation intervals, to be easily changed to comply with the standards of a particular country or application.

For troubleshooting purposes, the software also allows faults to be inserted in the system, using a password-protected function.