COMMUTATIONS

COMMUTATIONS

The laboratory is equipped with modern, state-of-the-art devices manufactured by DEGEM (Israel). Eight identical workplaces, two students per one (16 workplaces in total), enable instruction on practical devices. Students are enabled to simultaneously verify the theory, as well as to measure and analyze the characteristics of system parameters. There are Practicums for hands-on lab exercises. On the present equipment, it is possible to realize 40-50 different three-hour exercises in commutation and commutation systems.

This lab enables the analysis of principles of commutation and testing of all functions of commutation systems with space and time commutation. It also enables tracking of phases in making and breaking of temporary connections in a commutation system. In this lab, eight commutation systems are simultaneously configured and can be connected in pairs, which enables the realization of different connections in a system. The units have the same characteristics as the devices in commutation and transmission systems, which contributes to better understanding of their functioning.

Hybrid circuit in the unit is designed in hybrid technology by means of operational amplifiers and potentiometers. It enables the insight into the required conditions for minimizing the crosstalk in both directions of the transmission. Hybrid circuit is closed by the resistance from the resistance box which students choose during the measurement. It presents the basic requirements of signal measurement at an analogue level. Hybrid circuit is, together with all other elements of units, a part of a complex transmission system in its basic range.

ELT-2 is a unit which represents a unit of PCM terminal designed in accordance with ITU-TG.703. It contains codecs (coder-decoder), filters, multiplexer, clock signal extractor, line coder and decoder (compression law A), in accordance with ITU. The unit provides options for manual and automatic selection of time slots (E1 frame channels), thus it can be used for testing transmission in its basic range, as well as for testing commutation characteristics with time channel division. ELS-1 unit generates all signals which a real exchange produces. The unit simulates user circuits, trunk, tone generator and dial pulse counter.

TDM-PCM tester is a unit that enables students to access all distinct time slots within frame E1. It also contains a decoder with uniform characteristics, which enables the study of all features of compression according to Law A (in unit ELS-2).
By connecting units which enable microprocessor control it is possible to simulate an exchange with space and time commutation. The flow of a signal can be followed on monitors connected to a microprocessor unit.