AN93

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).

Answer Tone

 

 

 

 

 

 

 

 

 

(2225 or 2100 Hz).

Calling modem sends

Modem exchange packets.

Answering modem

training patterns and

 

 

packet(s).

 

 

sends training pat-

 

 

 

 

 

terns and packet(s).

 

 

 

Figure 68. Appearance of V.29 FastPOS Protocol

Rev. 1.3

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Image 285
Silicon Laboratories SI2494/39, SI2493/57/34/15/04 manual Appearance of V.29 FastPOS Protocol