INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : V.32 bis

Title : A duplex modem operating at data signalling rates of up to 
	14 400 bit/s for use on the general switched telephone network 
	and on leased point-to-point 2-wire telephone-type circuits

Study Group : XVII - Data Transmission over the Telephone Network

Version : New

Date of adoption : 1991

Notes :	


Recommendation V.32 bis presents a modem which is intended for use on 
connections on general switched telephone networks (GSTNs) and on 
point-to-point 2-wire leased telephone-type circuits. The principal 
characteristics of the modem are as follows:

	a) duplex mode of operation on GSTN and point-to-point 
	   2-wire leased circuits;

	b) channel separation by echo cancellation techniques;

	c) quadrature amplitude modulation for each channel with 
	   synchronous line transmission at 2400 symbols/s;

	d) the following synchronous data signalling rates shall be 
	   implemented in the modem:

	-   14 400 bit/s trellis coded,

	-   12 000 bit/s trellis coded,

	-   9600 bit/s trellis coded,

	-   7200 bit/s trellis coded,

	-   4800 bit/s uncoded;

	e) compatibility with Recommendation V.32 modems at 9600 and 
	   4800 bit/s;

	f) exchange of rate sequences during start-up to establish the 
	   data signalling rate;

	g) a procedure to change the data signalling rate without 
	   retraining.

Note 1 - On international GSTN connections that utilize circuits that 
are in accord with Recommendation G.235 (16-channel terminal 
equipments), it may be necessary to employ a greater degree of 
equalization within the modem than would be required for use on most 
national GSTN connections.

Note 2 - The transmit and receive rates in each modem shall be the 
same. The possibility of asymmetric working remains for further study.



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