3Com U.S. Robotics 56K Voice, Command Reference Manual

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Technical Specifications E-5
Flow Control
Requirements
If your computer and software support Clear to Send and you wish to use
Transmit Data hardware flow control (&H1), Pin 5 (DB-25) or Pin 8 (DB-9)
is required.
If your computer and software support Request to Send and you wish to
use Received Data hardware flow control (&R2), Pin 4 (DB-25) or Pin 7
(DB-9) is required.
For Macintosh
Computers
If you’re connecting your modem to a Macintosh computer, we strongly
recommend that you purchase a hardware handshaking cable to get the
most reliable performance.
Mac Pin Mac Pin Description Modem Pin Modem Pin Description
1 Output Handshake 4, 20 Request-to-Send and Data
Terminal Ready
2 Input Handshake 5 Clear-to-Send
3 Transmit Data - 2 Transmit Data
4 Ground 7 Ground
4, 8 Ground to Received
Data
5 Received Data - 3 Received Data