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CHAPTER 9: TECHNICAL INFORMATION
Packet Assembler Disassembler (PAD) Capabilities
The 7500 options provide capabilities comparable, but not identical, to those outlined in the CCITT
X.3, X.28, and X.29 specifications. The Local Mode commands provide the functions analogous to those
specified in X.28. The 7500 supports all X.29 messages received from a remote X.25 endpoint except the
Reselection PAD message.
7500 Options Relative to CCITT Recommendation X.3 Parameters: CCITT Recommendation X.3
defines certain parameters for an X.25 PAD. The CCITT assigns reference numbers by which these
parameters are identified and assigns different values to each parameter. The parameter values are also
represented by a number. The X.29 messages that the SET supports use these parameter reference
numbers and values. The Table below gives the parameter reference numbers and parameter values that
the 7500 supports. Parameter 101 is settable via X.29 but is not an X.3 parameter. Selected X.3
parameters and operations are supported as indicated by Table V. Other 7500 options that are not in
this table are not X.3 parameters and are not settable or readable via X.29.
Table V:
X.3 Parameters
Parameter
Parameter
Description
Reference
Number
Exit Data
1
Character
Echo
2
3
Selection of
data forwarding
character
4
Selection of
idle timer delay
Transmit Flow
5
Control
6
Control of PAD
Service Signals
7
Selection of operation
of the PAD on receipt
of Break signal
Discard
8
output
* R means the option value can be read via X.29.
** W means that the option can be written (set) via X.29.
144
Selectable
Possible
Values
0
Exit Data Disabled
1
Character DLE
2-15,17-127
As coded to ASCII
0
No echo
1
Echo
0
None
2
Carriage Return
126
All Control Characters + DEL
No Idle Timer
0
1-255
Value in twentieths of a second
0
None
1
Use of XON/XOFF
2
Use of EIA leads
0
Off
8
Verbose Mode
9
Numeric Mode
Break ignored
0
1
Interrupt
Reset
2
5
Interrupt and indicate break
Exit Data
8
21
Discard output, interrupt
and indicate break
Normal Data delivery
0
1
Discard output
Parameter
Meaning
R*
W**
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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