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CIRCUIT DESCRIPTION
49210 S
UBASSEMBLY
49210-00
LINE
1
LINE
2
TWO LINE
INTERFACE
P
6
AGE
Transformer
The transformer provides protective isolation between the line-
side facility and the module's modem tones-generating circuitry.
Eight-Lever DIP Switch
The switch provides programming for mode selection and
interface parameters (for example: data bits, stop bits, baud
rate, and so forth).
Regulated Power Supply
The power supply provides regulated +/-12 VDC and +/-5 VDC
output power for the module's circuits from -21 to -56 VDC input
power.
The subassembly's circuits consist of two ring detectors, two
line-select inputs, a line-switching relay, indicating LEDs,
control logic, and an over-ride switch.
Ring Detectors
Each of the two ring detectors provides ring detection for one of
the two lines. The output of a detector goes to a low (0 volts)
logic state when ringing voltage is detected on its associated
line. When there is no ringing voltage detected, the output
remains at a high (+5 VDC) logic state.
Line-Select Inputs
The line-select inputs control the line-switching relay. When the
line-select input for line 1 is grounded, (with input 2 open or at a
high logic level), the line-switching relay is OFF and line 1
remains connected to the 44210 modem. When the line-select
input for line 2 is grounded (with input 1 open or high), the relay
is ON and line 2 is connected to the 44210 modem. If both line-
select inputs are open or at a high level, the relay remains in the
state appropriate to the last selected line. If both line-select
inputs are grounded, the relay is OFF, and line 1 is connected to
the 44210 modem.
Line-Switching Relay
The relay is operated by the line-select inputs and is the dry-
contact type.
LEDs
Front panel LEDs are provided to indicate two things: which
line is currently connected to the 44210 modem and/or the
presence of ringing voltage. If an LED is ON continuously, it
indicates that line has been selected and is connected to the
44210 modem through the line-switching relay. If an LED is
44210/49210-0798 <90-00025>
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