User's Guide for ZyXEL Omni 56K USB Modem
3-5
Table 6. Physical Layer Capacity
STANDARD BIT RATE
[bps] BAUD RATE
[baud] MODULATION CARRIER FREQUENCY
[Hz]
V.90 28000-56000 8000 PCM 0
V.34 2400-33600 multiple TCM multiple
V.32bis 14400 2400 128-TCM 1800
V.32bis 12000 2400 64-TCM 1800
V.32bis 9600 2400 1800
V.32bis 7200 2400 16-TCM 1800
V.32bis 4800 2400 1800
V.32 9600 2400 32-TCM 1800
V.32 uncoded 9600 2400 16-QAM 1800
V.32 4800 2400 4-DPSK 1800
V.23 1200/75 1200/75 FSK
V.23 600/75 600/75 FSK
V.22bis 2400 600 16-QAM 1200 Call
2400 Ans
V.22 (BELL 212) 1200 600 4-DPSK 1200 Call
2400 Ans
V.21 (BELL 103) 300 300 FSK
Flow Control
This feature refers to stopping and restarting the flow of data into and out of the modem’s
transmission and receiving data buffers. Flow control is necessary so that a device does not
receive more data than it can handle. The Omni 56K USB provides two kinds of flow control
methods.
Hardware CTS/RTS Flow Control
This is a bi-directional flow control where CTS and RTS are simulated RS-232C signals that
must be available on your computer. When the modem’s transmission buffer is almost full, the
modem drops CTS to signal the DTE that it cannot accept data any more. Turn on the CTS to
notify the DTE that it can keep sending data to the modem. On the computer software side,
when the receiving buffer of the software is almost full, it drops RTS to signal the modem to
stop sending data to the DTE. Turn on the RTS and the modem starts sending data again to the
DTE.