TAM / TASM

An uncased working sample of a 100 line circuit Test Access Switch Matrix.

The assembled unit fits into an 19" standard cabinet or ETSI rack.

A second parallel card offers service protection should the card ever need changing. This is set up as a master/slave configuration and gives added protection on the circuit.

TASM Circuitry

An extra switch stage has been introduced to overcome the limitation of only being able to test one line circuit out of the 100 circuits available.

A two stage switch matrix is added as shown in the diagram to the right.

The first stage is split into four seperate 25 to 1 four wire matrix switches.

The output of each of these 25 to 1 switches is connected to the second stage switch, this allows the output to be switched to any 1 of 4 common TestBus Ports.

This makes it possible to switch one customer circuit in each group of 25 onto one of the four Test Busses simultaneously.

The 4 Test Bus Ports on each TASM are presented on pairs of RJ45 connectors. TestBus Ports from a number of TASMs are easily interconnected by simply daisychaining the ports together using standard Cat 5/Cat 5e network cabling. This cable then terminates at the Test Head.

A Test Head with four test bus inputs can still be a limitation on the system, it is possible to overcome this by adding more test heads across the TAM / TASM units. In practice four ports have been more than adequate across thousands of circuits by using a queuing method in the controlling circuitry.

Photos Coutesy of UTEL

Final Product - Master Card

Once housed the unit is fully protected and designed to fit into a dedicated rack mounting. The daisy chain from the test bus can be seen below.