Does this modem support Hardware CTS/RTS flow control?

Yes, this modem does have Hardware flow control.

The&K command controls this option:

Command:&Kn Flow Control Selection
Values: n = 0, 3, 4, 5, or 6
Defaults: 3 (data modem mode)
6 (fax modem and voice modes)
Description:&K0 Disables flow control.
&K3 Enables CTS/RTS hardware flow control.
&K4 Enables XON/XOFF software flow control.
&K5 Enables transparent XON/XOFF flow control.
&K6 Enables both CTS/RTS and XON/XOFF flow control.

With Hardware Flow Control, the modem uses its RS-232C interface to control the flow of data from the computer or terminal to which it is attached. The CTS (Clear to Send) signal on Pin 5 of the RS- 232C interface is brought low to stop the flow of data, and is brought high to restart it. When you select Hardware Flow Control as your Modem Initiated Flow Control method, you will also be selecting it for Pacing.
The difference between the two, however, is that Modem-Initiated Flow Control uses the Pin 5 CTS output signal, while Pacing uses the Pin 4 RTS input signal.

note: For hardware pacing, make sure you provide the pin 4 RTS signal.

The MT5600ZDX owner's manual can be downloaded from our Website at:

http://www.multitech.com/en_US/DOCUMENTS/Families/MultiModemZDX/manuals
(it is found in the Archived Manuals section)