Packet Assembler Disassembler (Pad) Capabilities - AT&T 7506 User Manual

Pin 20 — Data Terminal Ready (CD)
This circuit allows the attached terminal to control the connection of the ADM to the network.
When the DTR option is set to FOLLOW, the ADM requires an ON condition to interact with the
attached terminal or to initiate or maintain a data connection or test sequence (except the local
self-test). If the attached terminal drops DTR for more than 50 milliseconds during data call
setup, while in the data transfer mode, or during a test sequence, the ADM clears the call or
terminates the test.
When the DTR option is set to IGNORE, the ADM ignores the DTR lead. Thus, dropping the
DTR lead will not cause a call to be cleared.
Pin 22 — Ring Indicator (CE)
A pulsed signal appears on this circuit when the data terminal receives an incoming data call.
This signal is maintained until the data terminal answers or clears the call, or until the network
clears the call attempt. The cadence is designed to simulate ringing: two seconds on and four
seconds off. The initial pulse remains on for a minimum of one second.

Packet Assembler Disassembler (PAD) Capabilities

The ADM options provide capabilities 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
ADM supports receipt of X.29 SET and READ parameter messages received from a remote
X.25 host.
Receipt of an X.29 SET command with no parameters (defined by CCITT to mean ''load initial
profile'') causes the ADM to restore the PAD parameter values which were active at the start of
the data call.
ADM 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. Table 6-1 gives the
parameter reference numbers and parameter values that the ADM supports. Parameter 101 is
settable via X.29 but is not an X.3 parameter. Other ADM options that are not in this table are
not X.3 parameters and are not settable or readable via X.29.
Technical Information 6-3