Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
4.3 PHYSICAL SLOTS AND TIME SLOTS
As discussed above, a given channel module (depending on its function) may use one or more of the
twenty-four 64-Kbps time slots provided by each direction of a E1 circuit. In addition, a given channel
module may be assigned to any available time slot (or group of time slots) within a E1 circuit,
regardless of its physical location (slot) on an IMUX 2000 equipment shelf. This makes it important to
distinguish physical slots on IMUX 2000 multiplexer shelves from time slots within the E1 circuit. In
most cases, they are not directly related.
4.3.1 CHANNEL DIRECTION AND RELATIONSHIP TO CM4 MODE
Channel modules can be set to transmit in either "Direction A" or "Direction B". The transmit and
receive directions are always opposite from one another. This means that a channel module set to
transmit in Direction A will receive from Direction B. If the channel module is set to transmit in
Direction B, it will receive from Direction A. Every channel module has a switch that sets its
transmit/receive direction. Consult the Instruction Data Sheets in Sections 15 through 19 of this
manual to determine the location and labeling of this switch on any given module.
Each CM4 Common Module operates in one of three modes: TERM, DI-A or DI-B (See Section 6 of
this manual for more information on CM4 modes). CM4 modules operating in either the DI-A or
TERM mode take the transmit data from channel modules set to transmit in Direction A, and multiplex
it together for transmission on the outgoing E1 line in Direction A. CM4 modules operating in the DI-
B mode take the transmit data from channel modules set to transmit in Direction B, and multiplex it
together for transmission on the outgoing E1 line in Direction B.
Figure 4-1 illustrates this process. In terminal multiplexers, only Figure 4-1a applies; all channel
modules in a terminal multiplexer must be set to transmit in Direction A and receive from Direction B.
In drop/insert multiplexers, channel modules can be set to transmit in either direction. The channel
modules set to transmit in Direction A and receive from Direction B will work according to Figure 4-
1a; Figure 4-1b shows how the channel modules set to transmit in Direction B and receive from
Direction A will work.
Note the "CTL" connection on Figure 4-1. This is a control wire. When a channel module set to time
slot N is active in a drop/insert multiplexer, the control wire carries a signal that tells the CM4 to place
local data (from the channel module) instead of through data (from the incoming E1 signal) into time
slot N of the outgoing E1 signal.
IMUX 2000E1 RFL Electronics Inc.
January 1, 2008 4-2 (973) 334-3100
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