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LEGAL INFORMATION
A.4 The X.21 Interface
Here is the ITU-T X.21 pinout for the FradSwitch A/S 3 Port’s X.21 main-link-
ports, both unadapted (pinned out as per RS-530 on DB25) and patched with
adapter cable (pinned out on standard DB15).
ITU-T RS-530
V.35
Signal
Signal/Lead Name
V.24
(DB25)
Adapter
Abbrev.
Circ.
Pin
(M/34)
Ref.
Pin
101
1
1
––
Frame Ground
102
7
8
G
Signal Ground
103
2
2
T A
Trasnmit A
14
9
T B
Transmit B
104
3
4
R A
Receive A
16
11
R B
Receive B
105
4
3
C A
Control (Request tio Send) A
19
10
C B
Control (Request tio Send) B
109
8
5
I A
Indication (Carrier Detect) A
10
12
I B
Indication (Carrier Detect) B
113
24
7
E A
External Signal Element Timing (External Clock) A*
11
14
E B
External Signal Element Timing (External Clock) B*
114
15
6
S A
Signal Element Timing (Transmit Clock) A
12
13
S B
Signal Element Timing (Transmit Clock) B
*The E A and E B signals are not included in the standard X.21 interface. On the Switch, these
signals (which provide the external clocking option that X.21 otherwise lacks) are substituted for
the Byte Timing (B A and B B) signals, which are rarely if ever used.
A.5 The DDS Interface
Here is the pinout for the DDS main-link port (Port 1, the modular RJ-48 socket)
on “-DDS” models of the FradSwitch A/S 3 Port. All unlisted pins are unused.
DDS
Signal/Lead Name
(RJ-48)
Pin
1
Receive (RX) Ring
2
Receive (RX) Tip
4
Transmit (TX) Ring
5
Transmit (TX) Tip
