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CHAPTER 9: TECHNICAL INFORMATION
7500 — Asynchronous DTE
Attached Data Communications Equipment
Attached data communications equipment communicating via asynchronous 10-bit transmission
including parity bit, 1 start bit, and at least 1 stop bit. For local mode operation and data call control
the character code set must be ASCII. Single speed modems must provide no connection to the speed
indication control leads on pins 12 and 13 of the interface. Dual speed modems must provide
connection to the CI lead and no connection to the CI2 lead. Triple speed modems must provide speed
indication control leads CI and CI2.
Data Rates
The 7500 operates at asynchronous full-duplex rates of 300, 1200, 2400, 4800, 9600, and 19200 bps.
DTE EIA Interface Information
The 7500 provides a female EIA-232D receptacle. Where this product employs the EIA-232D
standard interface, older equipment which adheres to the RS-232C standard can also be connected. The
EIA customer interface pin assignments are listed in table below.
Asynchronous DTE Pin Assignments
Table O:
Pin 2 - Transmitted Data (BA)
Signals on this lead are transmitted by the 7500 to the attached modem. This lead is held in the
MARK state (logic level 1) when data is not being transmitted.
In the Data Mode, data transmitted to the modem will consist of one start bit, eight information bits
and one stop bit. The parity of data received from the network will be sent to the modem without
alteration. A break signal is transmitted to the modem in response to an Indication of Break X.29
message received from the network. The break signal consists of binary zero bit transmission for more
than 135 msec followed by binary one bit transmission for more than 100 msec.
132
PIN
CIRCUIT
NO.
MNEMONIC
BA
2
BB
3
CA
4
CB
5
CC
6
AB
7
C F
8
12
C I
CI2
13
18
CN
CD
20
R L
21
CE
22
25
TM
DESCRIPTION
Transmitted Data
Received Data
Request to Send
Clear to Send
Data Set Ready
Signal Ground
Received Line Signal Detect
Speed Mode Indicator
Speed Mode Indicator
Analog Loopback
Data Terminal Ready
Remote Loopback
Ring Indicator
Test Mode
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