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4. The analog-end modem answers and completes the call:
If the modems are compatible, the end-to-end connection will be complete, and data exchange
can take place.
If the modem in the modem pool is a multi-speed modem and the modem-to-modem handshake
results in the modem pool modem falling back in speed, this indication is signalled to the 7500
via pins 12 and 13 of the EIA interface. See CHAPTER 9: TECHNICAL INFORMATION for
pins 12 and 13.
5. After the call has been established, the user on the analog side can use the commands listed on
the next page to change 7500 options for the duration of the call. The options that can be
changed are described in complete detail in CHAPTER 4: DEFINITIONS OF 7500 OPTIONS.
If Local Mode is off, then options cannot be changed.
7500 Modem Pool: Analog to Digital Network
Local Mode must be set to cmd or at for analog to digital circuit switched modem pooling.
1 . In the case of the 5ESS switch X.25 packet data modem pool, the user on the analog network
dials the telephone number associated with the data device that is connected to the digital
network. The digital user must subscribe to this number for receiving data calls. Otherwise, the
analog user dials a modem pool hunt group telephone number.
2. The modem signals the 7500 that a call has arrived from the analog side by toggling the Ring
Indicator lead.
3. The 7500 signals the modem to answer the call by turning on the DTR lead.
4. In the case of the 5ESS switch X.25 packet data modem pool, the modem answers and the 7500
initiates an X.25 packet data call (Zero Called Address option is on). The network automatically
routes the call. Otherwise, the 7500 sends a [ CMD: ] prompt to the user on the analog side. The
user must then type dial and the dialed number of the endpoint.
If the modem in the modem pool is a multi-speed modem and the modem-to-modem handshake
results in the modem pool modem falling back in speed, this indication is signalled to the 7500
via pins 12 and 13 of the EIA interface. See CHAPTER 9: TECHNICAL INFORMATION for
pins 12 and 13.
5 . The user on the analog side can use the commands listed on the next page to change 7500
options for the duration of the call, provided the Local Mode option is set to cmd. The options
that can be changed are described in complete detail in CHAPTER 4: DEFINITIONS OF 7500
OPTIONS
Disconnecting a Data Call from Either Endpoint
Either the analog or the digital endpoint can terminate a data call, no matter who has initiated the
call.
Analog Disconnect
When the analog side disconnects the call, the attached modem turns off the DCD (Data Carrier Detect)
or DSR (Data Set Ready) lead and the 7500 clears the data call.
Digital Disconnect
When the user on the digital side disconnects the call, the data call is cleared, and the 7500 turns off
the DTR (Data Terminal Ready) lead to notify the modem to end the analog side of the call.
CHAPTER 6: ASYNCHRONOUS DTE CONFIGURATION
97
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