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PROGRAMMABLE SECURITY GUARD
4.4 RS-232 Control Leads Supported
Table 4-1 lists the control leads supported by the
PSG and when they are used.
DB9
PIN
INPUTS
3
2
RXD
7
8
CTS
6
5
GND
1
DCD
4
9
RI
NOTE: The PSG comes with 2 DB9 ports. DB9-to-
DB25 adapter cables (straight and cross) are
available separately.
4.5 Modem Control Procedures and Timing
Requirements
4.5.1 A
I
NSWERING AN
NCOMING
The PSG will detect incoming calls on either port.
The RS-232 signal "RI Active" indicates that the
attached modem is receiving an incoming call. After
the PSG recognizes two rings, it will raise DTR to
the modem. This allows the modem to answer
automatically according to the modem's preset
number of rings, unless the PSG is in the middle of
a callback sequence. After the PSG raises DTR, DCD
input must become active within one minute to
indicate a successful connect with another modem.
Otherwise, the unit will reset to Security Mode.
24
Table 4-1. RS-232 Control Leads Supported.
OUTPUTS DESCRIPTION
TXD
Transmit Data
Receive Data
RTS
Request to Send
Clear to Send
DSR
Data Set Ready
GND
Signal Ground
Data Carrier Detect
DTR
Data Terminal
Ready
Ring Indicator
C
ALL
WHEN USED
Driven with TX data
Monitored for RX data
Always active
Monitored when hardware
flow control is used
Jumper-selectable active or open
Reference signal
Monitored when modem
controls are used
Toggles when hardware flow
control or modem control is used
Monitored when modem
controls are used
4.5.2 D
ISCONNECTING AT A
The PSG will monitor DCD input to detemine when
a call is disconnected (DCD must go from active to
inactive). When DCD input goes inactive for 10
milliseconds, the PSG will assume that the call has
been disconnected.
4.5.3 D
ISCONNECTING A
M
ODEM
The PSG will drop its DTR output signal upon
receiving the exit command to disconnect a call.
DTR output will stay inactive for at least two seconds
to assure that the call terminates.
R
M
EMOTE
ODEM
C
L
ALL FROM THE
OCAL
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