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Table 3-D.
Group 4 Internal
Clock Rate Divide
Ratio
(C) Closed (O) Open
Rate
0
1
2
3
4
5
6
7
8
9
In Group 4, the Rate Switches select the divider ratio for this oscillator. Refer to
Table 3-D and Section 3.3.2 for more details.
3.3.1 Standard Internal Clock Rates (Groups 1, 2 and 3)
If the data rate appears in Table 3-C, select the corresponding internal clock group with
the mode switches (refer to Table 3-A). Then set the Rate Switches to complete the rate
selection process.
3.3.2 Custom Internal Clock Rates (Group 4)
The Group 4 Internal Clock Mode can be used if an oscillator has been specified or
installed in the custom oscillator socket (refer to Section 2.1.6). The available
oscillators and their respective clock frequencies are given in Table 3-E. If the rate
appears in table, choose the appropriate oscillator option for the modem.
Obtaining the desired divide ratio may require changing the position of the TBL /
NORM DIP switch as shown in Table 3-D. The location of the TBL / NORM switch
is shown in Figures 2-3 and 3-4.
DIP Switches
Rate Switches
Normal and Alternate Table
1
2
3
4
NORM (ON) * TBL (OFF)
C
C
C
C
4
O
C
C
C
8
C
O
C
C
16
O
O
C
C
32
C
C
O
C
48
O
C
O
C
96
C
O
O
C
192
O
O
O
C
384
C
C
C
O
64
O
C
C
O
128
* Factory setting
2240 Fiber Optic Modem
Group 4 Divide Ratios
16
32
64
128
768
1536
3072
6144
256
512
33
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