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To Connect:
1. CPU operator closes the dedicated (leased) line in the
program, opens the switched network line, and sets
the 3872 to 2400 SWITCHED.
2. By prearrangement or by separate phone call, the CPU
operator alerts the terminal operator to change to
SNBU operation and call the number of the CBS/3872
at the CPU, from the telephone attached to the CDT
at the terminal.
3. Terminal operator sets the 3872 to TALK and 2400
SWITCHED, makes the terminal ready, and dials the
call.
4. Terminal operator, upon hearing the end of the
answer tone, pulls up the data key on the cradle of
the CDT telephone, switches the 3872 to DATA, and
data transfer begins.
To Disconnect:
1. By prearranged recognition of completed data transfer
or by separate phone call, the operators agree to dis-
connect.
2. CPU operator closes the switched network line in the
program.
Note: Connection of unexpected incoming calls may be
avoided by setting the 3872 Modem to TALK.
3. Terminal operator disconnects by cradling (hanging up)
the handset of the telephone attached to the CDT.
Manual Answering (CDT DAA) at CPU and Automatic
Answering (CBS Data Coupler) at Terminal
Control of the 'data terminal ready' interface line must be
effected at the terminal. The cable from the second
(switched network) interface of the dual communications
interface must be plugged into the 3872, or the terminal
program must be reloaded for switched network operation.
(Figure C-4).
To Connect:
1. CPU operator closes the line in the program and, by
prearrangement or separate telephone call, alerts the
terminal operator that SNBU operation will be used.
2. Terminal operator makes the necessary changes for
switched network operation, sets the 3872 to 2400
SWITCHED, and makes the-terminal ready.
3. CPU operator sets the 3872 to TALK and 2400
SWITCHED and, using the telephone attached to the
CDT, calls the number of the CBS/3872 at the termi-
nal.
4. Upon hearing the end of the answer tone, the CPU
operator pulls up the data key on the cradle of the
CDT telephone and sets the 3872 to DAT A.
5. CPU operator opens the line in the program and enters
any CPU console message necessary to start data
transfer.
To Disconnect:
1. By prearranged recognition of the end of data transfer
or by a separate telephone call, the operators agree to
disconnect.
2. CPU operator closes the line in the program and cradles
(hangs up) the telephone attached to the CDT.
3. Terminal operator disconnects by disabling the terminal
or by setting the 3872 to TALK.
Note: At a dual interface terminal that has not been re-
programmed, the operator must disconnect by setting
the 3872 to TALK. Connection of unexpected incoming
calls may be avoided by setting the 3872 Modem to TALK.
Automatic Answer (CBS Data Coupler) at Both Ends
Control of the 'data terminal ready' interface line must be
effected at both ends. At the CPU, the program data path
may have to be changed and the cable to the 3872 Modem
may have to be changed (Figure C-3). At the terminal, the
cable from the second interface of the dual communications
interface must be plugged into the 3872 Modem (unless it
is already connected to a 3872 with the Fan-Out feature),
or the terminal program will have to be reloaded for switched
network operation (Figure C-4).
To Connect:
1. CPU operator closes the dedicated (leased) line in the
program and opens the switched network line.
2. By prearrangement or by separate telephone call, the
operators arrange for SNBU operation and for data
transfer. The 3872 Modems are both set to 2400
SWITCHED.
3. Terminal operator makes the necessary changes for
switched network operation and makes the terminal
ready.
4. Calling operator sets the 3872 to TALK, lifts the hand-
set of the telephone attached to the CBS, pulls up the
exclusion key on the telephone cradle, and dials the
number of the CBS/3872 at the other end.
5. Upon hearing the end of the answer tone, the calling
operator sets the 3872 to DATA and cradles (hangs up)
the handset when the answer tone ends. Data transfer
begins.
To Disconnect:
Note: Connection of unexpected incoming calls may be
precluded by setting the 3872 Modem to TALK.
1. By prearranged recognition of the end of data transfer
or by separate telephone call, the operators agree to
disconnect.
2. CPU operator closes the switched network line in the
program.
3. Terminal operator disconnects by disabling the terminal
or by setting the 3872 to TALK.
Note: At a dual interface terminal that has not been re-
programmed, the operator must disconnect by setting the
3872 to TALK.
Appendix C. Switched Network Backup with BTAM
C-5
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