S1 through S3: Data Rate Setting
Switches S1 through S3 are set in combination to determine the
synchronous data rate for the Model 1205. Switch S4 is not active.
S1
S2
S3
S4
Setting
Off
Off
Off
N/A
32 kbps
(factory default)
On
Off
Off
N/A
48 kbps
Off
On
Off
N/A
56 kbps
On
On
Off
N/A
64 kbps
Off
Off
On
N/A
72 kbps
On
Off
On
N/A
112 kbps
Off
On
On
N/A
128 kbps
On
On
On
N/A
144 kbps
3.3 INTERNAL JUMPERS
The Model 1205 has three pairs of jumpers (JP1, JP2 and JP3)
mounted on the internal PC board. See Figure 3, below. These
jumpers set clocking, carrier, and RTS/CTS delay independently for
ports A and B.
Figure 4 (following page) presents a detailed view of JP1, JP2 and
JP3, and also shows the factory default setting for each jumper. Please
observe that each pair contains one strap to configure Port A and one
strap to configure Port B. Observe also that each strap has three
possible positions: covering posts 1 & 2, covering posts 2 & 3, or
removed altogether. The detailed description for each pair of jumpers
presents all valid strap position options.
5
Figure 3.
Model 1205 Jumper Orientation and Factory Default on Internal PC Board.
JP3
JP1
JP2
PORT A
PORT B
PORT B
JP1: RTS/CTS Delay
The setting for jumper JP1 determines the amount of delay
between the time the Model 1205 “sees” RTS and when it sends CTS.
In order to emulate either dial-up or leased line modems, you can set
this strap at either 0 msec, 7 msec or 53 msec.
Note
: Port A and Port
B must be configured separately. Jumper functions are identical.
JP1
Setting
Position 1&2
7 msec Delay
(factory default)
Position 2&3
53 msec Delay
Strap Removed
0 msec Delay
JP2: Carrier Control
The setting for jumper JP2 determines whether the Model 1205’s
carrier is “constantly on” or “controlled by RTS”.
Note
: Port A and Port
B must be configured separately. Jumper functions are identical.
JP2
Setting
Position 1&2
Carrier “Controlled by RTS”
Position 2&3
Carrier “Constantly ON”
(factory default)
Strap Removed
Not a Valid Setting
JP3: Clock Source
The setting for jumper JP3 determines whether clocking is internal,
external or received loopback.
Note
1
: Only port A may be set for
external clock.
Note
2
: If Port B is set for receive loopback clock, Port A
must be set for external clock. Port B may not be set for external clock.
JP3 (Port A)
Setting
Position 1 and 2
Internal Clock
(factory default)
Position 2 and 3
External Clock
Strap Removed
Not a Valid Setting
JP3 (Port B)
Setting
Position 1 and 2
Internal Clock
(factory default)
Position 2 and 3
Received Loopback Clock
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Figure 4.
Detailed View of Model 1205 Jumpers Showing Factory Default Settings
Port A
Port B
Port B
Port B
Port A
Port A
JP3
JP2
JP1
1 2 3
1 2 3
1 2 3
1 2 3
1 2 3
1 2 3