User`s manual

Installation
16 User’s Manual - DSP19.2 Fast Poll Modem
RTS signal. If you enable constant carrier (switch S1-6 = 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 S1-6 = OFF), the RTS-CTS delay is 23 ms for 2400 bps
and above.
S1-7 − 2 or 4-Wire Operation
y S1-7 ON = 2-Wire, Half-Duplex Mode
y S1-7 OFF = 4-Wire, Full-Duplex Mode (default)
Switch S1-7 configures the modem for either 4-wire full-duplex or 2-wire half-duplex
operation.
S1-8 − Transmitter Impedance
y S1-8 ON = Switched by RTS
y S1-8 OFF = 600 Ω (default)
Switch S1-8 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.
This configuration should be used for all slave modems to prevent the transmitting modem
from being unnecessarily burdened. To select this configuration, set switch S1-8 ON for the
slave modems.
If you use the modem with transmission lines that are transformer-coupled or with an
impedance-isolated network (such as a transformer bridge), set switch S1-8 OFF for proper
operation.
S1-9 − Remote Loopback Enable
y S1-9 ON = Loopback enabled
y S1-9 OFF = Loopback disabled (default)
During instances of channel noise, the modem may mistake a received preamble as a
request to go into remote digital loopback. Setting switch S1-9 to OFF prevents the modem