ComStream CM601, Installation And Operation Manual

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3-2 External Connections
EIA RS-449 Electrical Specifications
The EIA RS-449 electrical specifications are shown in Table 3-2 for differential
(RS-422) and single-ended (RS-423) drivers and receivers.
The differential pair has a true signal, indicated by a B, and an inverted signal,
indicated by an A. These two differential signals must always be opposite in
polarity. With no line attenuation, each signal should be within ±1.5 V of the
nominal level, which is approximately 2.5 V above signal ground. Driver and
receiver impedance are included for reference only.
The CM601 data connector is pinned out as data communications equipment
(DCE); therefore, the user data equipment must be configured as data terminal
equipment (DTE) in order to make a straight cable between them.
Table 3-2 Electrical Specifications for Differential (RS-442) and Single-Ended
(RS-423) Drivers and Receivers
Driver Specifications
Differential Driver
(Output) B – true signal, 0 or 5 V
A – inverted signal, 5 or 0 V
Less than 100 ohms between A and B
Single-Ended Driver
(Output) Greater than +3 V or less than -3 V with respect to signal ground
Less than 50 ohms with respect to signal ground
Differential Receiver
(Input) B – true signal, 0 or 5 V
A – inverted signal, 5 or 0 V
100 ohms between A and B
Single-Ended Receiver
(Input) Greater than +3 V or less than -3 V with respect to signal ground
Minimum 4 kohms signal to ground