Installation
15 User’s Manual - SM202T/SMV23 Modem
SW1-4 – Soft Carrier Control
x SW1-4 ON = Soft Carrier is enabled
x SW1-4 OFF = Soft Carrier is disabled
In Bell 202T mode, when soft carrier mode is enabled, a carrier frequency of 900 Hz is
transmitted at the end of a transmission in order to turn off the carrier detect (CD) at the
receiving modem. This feature is only use for the Bell 202T modems.
SW1-5 Anti-streaming
x SW1-5 ON = Anti-streaming is active
x SW1-5 OFF = Anti-stream is inactive (default)
Typically, anti-streaming is used in multi-point applications to prevent a malfunctioning slave
data terminal or RTU from occupying the line indefinitely. When anti-streaming is active, the
modem can transmit data for a maximum of 30 seconds before the transmitter turns off
automatically. The modem then looks for an ON-to-OFF RTS transition before proceeding
with normal operation.
SW1-6 2-Wire or 4-Wire Operation
y SW1-6 ON = 2-Wire, Half-Duplex Mode
y SW1-6 OFF = 4-Wire, Full-Duplex Mode (default)
Switch SW1-6 configures the modem for either 4-wire full-duplex or 2-wire half-duplex
operation.
SW1-7 Transmitter Termination Impedance
y SW1-7 ON = Switched by RTS
y SW1-7 OFF = 600 : (default)
Switch SW1-7 is used for multi-point configuration networks. When multiple modems are
connected on the same metallic circuit:
y The transmitter termination should be of high impedance if the modem is not
transmitting in order not put a load on the line.
y The transmitter is only terminated with 600 ohms when RTS is asserted.
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