Installation
14
User’s Manual - SM202T/SMV23 Modem
SW1-1
Auto RTS
y
SW1-1 ON = Enable Auto RTS
y
SW1-1 OFF = Disable Auto RTS (
default
)
For data terminals that do not provide hardware Request To Send (RTS), set switch SW1-1
to ON to enable auto RTS mode. In this mode, TXD is detected at the modem and an
internal RTS signal is turned ON. After training completes, the TXD is transmitted to the
remote modem. The transmitter turns itself off if no TXD is detected after a pre-determined
length of idle time.
SW1-2
RTS-CTS Delay (Bell 202 Mode Only)
y
SW1-2 ON = 33.0 ms delay
y
SW1-2 OFF = 10.0 ms delay (
default
)
Switches SW1-2 determines the duration of the RTS-CTS delay in Bell 202 mode. For V23
mode, the RTS-CTS delay is fixed at 33 ms.
SW1-3
Transmit Carrier Control
y
SW1-3 ON = Constant carrier
y
SW1-3 OFF = Controlled by RTS (
default
)
Switch SW1-3 selects either constant or switched carrier. Constant carrier allows DTEs,
such as asynchronous terminals or RTUs, to operate with modems, without requiring an
input RTS signal. If you enable constant carrier (switch SW1-3 = ON), the modem forces the
transmit carrier active and the RTS-CTS delay is shortened to less than 0.5 ms.
You can use constant carrier in 4-wire point-to-point, or at the master unit of multi-point
network applications to reduce modem training time.
In switched-carrier mode (switch SW1-3 = OFF), the RTS-CTS delay is determined by SW1-
2 setting.