Specifications

SW3 DIP Switch Settings
SW3 is a 10-position DIP switch. Table 2-5 shows the modem switch settings for DIP switch SW3. A description of
the SW3 switch settings follows the table.
Table 2-5. Modem Switch Settings for DIP Switch SW3
Switch Settings Switches
ON OFF (Default)
SW3-1: Fast Poll/FSK (page 14) FSK Fast Poll Auto-Rate
SW3-2: Data Rate (page 15) 4800 bps 9600 bps
SW3-3: Async Character (page 15) 11 bits 10 bits
SW3-4: Auto RTS (page 15) Enabled Disabled
SW3-5: Transmitter Termination (page 15) Switched by RTS
600 Ω
SW3-6: Reserved (Test Only) (page 16) Test Normal
SW3-7: 2- or 4-wire (page 16) 2-wire, half-duplex 4-wire, full-duplex
SW3-8: Carrier Control (page 16) Constant Switched
SW3-9: Rx Termination (page16)
600 Ω
High Rx Impedance
SW3-10: Signal Ground and Earth Ground Option (page 16) Connected Separated
SW3-1 − Fast Poll Auto Rate/FSK
SW3-1 ON = Low-Speed Mode (FSK)
OFF = High-Speed Mode (Fast Poll)
The modem has two operating modes:
 FSK mode, which supports data rates from 0 to 1800 bps.
 Fast-poll mode, which supports data rates of 4800 and 9600 bps.
SW3-1, along with the Data Rate Selector (DRS) pin on the modem’s RS-232 connector, configures the modem for
either FSK or fast-poll mode. Table 2-6 shows how SW3-1 and the DRS signal configure the modem for these
operating modes.
Table 2-6. Modem Operating Mode
To Select… Set SW3-1 to… And the DRS Signal…
Fast-poll mode OFF Is not connected or is set HIGH
FSK mode OFF Is set LOW
FSK mode ON Doesn’t care
You should use the DRS signal in RTS control mode. It does not work in either constant carrier mode (SW3-8 set to
ON) or in the auto-RTS mode (SW3-4 set to ON). The DRS signal is only sampled when the transmitter is idle
(when not sending a preamble, data, or a turn-off sequence).
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