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High-Speed Interface
Line Descriptions
The IBM 3704 and 3705 Communications Controllers high-speed interface
provides for the attachment of an external high-speed modem for operation on
wideband services at speeds up to 50,000 bps.
The interface is a cable terminated with a Burndy MD 12 MXP-17TC (or equiva-
lent) coaxial plug, which interfaces to a Burndy MD 12 MXR-8T coaxial connec-
tor. The cable consists of 12 coaxial circuits and has a maximum length of 50 feet.
The interface lines and pin assignments are as follows.
Pin
Circuit
A
Not Used
B
Not Used
c
Clear to Send
D
Send Request
E
Send Data
F*
Data Set Ready
F**
Ring Indicator (see note)
G
Local Test
H
Not Used
J
Serial Clock Transmit
K
Receive Data
L
Serial Clock Receive
M*
AGCLock
M**
Data Terminal Ready (see note)
* Denotes center pin
** Denotes shield
Note: These leads are EIA RS-232 voltage mode circuits.
Signal Ground. The signal ground connection is completed between the IBM
3704 and 3705 and the modem through the coaxial shield leads (with the excep-
tion of Ring Indicator-Pin F, and Data Terminal Ready-Pin M). This line is
used to establish the reference potential for all signal lines and is connected to 0
volts in the IBM 3704 and 3705 power supply.
Clear to Send (CTS). The modem generates signals on this circuit, that indicate
to the IBM 3704 and 3705 that the modem is transmitting the information present-
ed on the Send Data line. The modem must turn ON the Clear to Send line in
response to an ON condition on the Request to Send line.
Send Request (SR). The Send Request line from the IBM 3704 and 3705 is a
request for the modem to transmit data, presented on the Send Data line, to the
remote terminal. When the IBM 3704 and 3705 brings up Send Request, the
modem must respond with a Clear to Send signal and must then transmit the data
presented on the Send Data line.
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IBM 3704 and 3705 Communications Controllers Original Equipment Manufacturers' Information
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