Model 458-SM-2-16 Transparent Switching Module
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2.2
Operation as a Multiplexer
The front of the Switching Module contains sixteen RJ-45 connectors in two groups of eight RJ-45’s. Therefore, each
Switching Module can accept and multiplex up to sixteen independent incoming differential lines to one or two outgoing
differential lines.
The rear of the Switching Module has two R-J45 Output Connectors where each connector can be assigned to one
differential Input Signal. Therefore, two of the sixteen Input Signals can be multiplexed to the two Output Connectors,
and the two Switching Module outputs can be directly connected to two independent channel inputs of the Telebyte
family of Local Loop Simulators, or other similar devices.
The Switching Module operates in three possible modes:
In the first mode, the Output Channel 1 RJ-45 rear connector can select any of the16 incoming lines (Input
Signals) from the 16 RJ-45 front connectors. Selection of incoming lines 9 through 16 is allowed only when
the Output Channel 2 rear RJ-45 connector path is disabled.
In the second mode, the Output Channel 2 RJ-45 rear connector can select any of the16 incoming lines (Input
Signals) from the 16 RJ-45 front connectors. Selection of incoming lines 1 through 8 is allowed only when
the Output Channel 1 rear RJ-45 connector path is disabled.
In the third mode, the block of 16 incoming lines (Input Signals) are partitioned into two groups of 8 signal
inputs. The Output Channel 1 RJ-45 rear connector can select any of the incoming lines 1 through 8, and the
Output Channel 2 rear RJ-45 connector can simultaneously select any of the incoming lines 9 through 16.
Switching between modes is permitted only when the specified Output Channel is selected. This prevents a channel from
being discontinued when not specified in a command. Therefore, when switching modes it may be necessary to disable
the other channel (see Truth Table).
The selection and control of the paths from input to output is through firmware installed on the Telebyte 458-CM that is
associated with the 458-CC-16 (16-Slot) chassis, or on the 458-3SL/3SLA (3-Slot) chassis. The commands are provided
in the Appendix. The basic command consists of three numbers:
The physical slot location of the Module in the chassis to be changed. The location of slot 1 is at the left side
of the 458-CC-16 (16-Slot) chassis and is the top slot of the 458-3SL/3SLA (3-Slot) chassis.
The Output Channel (output connector 1 or 2) that the signal is to go to. The location of Channel 1 is the
upper connector at the rear of the Switching Module.
The Input Signal (1 through 16) that is to be selected to go to the selected Output Channel, including no
signal. Input Signal 1 is the upper RJ-45 connector of the upper RJ-45 block, and Input Signal 16 is the
bottom RJ-45 connector of the lower RJ-45 block on the front of the Switching Module.
The same Input Signal of each of the sixteen inputs is prevented from being routed to more than one Output Connector by
two different control systems, which prevents impedance division.
The Matrix Block relay logic is configured as an ‘exclusive or’ (XOR) so that only one input can be switched
to only one output.
The firmware logic that controls the selection prevents the selection of more than one input of the group for
each output, and prevents the input from use at any other output.
