Installation
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).
Note that DRS controls both the transmitter and receiver. If DRS changes states while the modem is receiving a preamble, data, or a turn-off sequence, the state of the receiver is unknown until the carrier drops and a new preamble is received. We recommend that DRS does not change states until both the local and remote modems’ transmitters are in the idle state. When they are, both the local and remote modems’ DRS signal should change states.
