SI2457-D-FT Silicon Laboratories Inc, SI2457-D-FT Datasheet - Page 285

• Manufacturer Part Number: SI2457-D-FT
• Description: IC ISOMODEM SYSTEM-SIDE 24TSSOP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2457-D-FT

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

As shown in Figure 68, the V.29 FastPOS protocol looks different than the older, slower V.22-like protocols. It is
also half-duplex, and each participating modem uses the entire spectral space available on the telephone line.
A receiving modem recognizes that the calling modem is V.29-capable by detecting the V.29 calling tone at 980 Hz.
Another example with some more SDLC-oriented data is provided later in this document.
DTMF dialing.
V.29 Calling
Tone (980 Hz).
Figure 68. Appearance of V.29 FastPOS Protocol
(2225 or 2100 Hz).
Answer Tone
Answering modem
sends training pat-
terns and packet(s).
Rev. 1.3
Calling modem sends
training patterns and
packet(s).
Modem exchange packets.
AN93
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