Maxim Integrated Teridian V.22 bis Linux Softmodem for 73M1822/73M1922 MicroDAA - Manual (Page 15)

V.22BIS Linux Softmodem for 73M1x22 MicroDAA User Guide UG_1x22_043
15 Rev. 1.4
V Verbose/Numeric Result Codes Selection
V0 Numeric result codes – Format digit(s)

V1 Verbose result codes – Format word
V2 Numeric result codes - Format digit(s)
Refer also to the Q[n] and X[n] commands
Y Asynchronous/Synchronous Mode Selection
Y0 Asynchronous mode. No speed buffering, no protocol.
Y1 Synchronous mode. No speed buffering, no protocol.
Y4 Quasi-Synchronous mode. Allows the transmission and reception of
synchronous data through an asynchronous DTE by stripping off start and stop
bits on transmission and adding them on reception (See V42 operation).

Y6 Asynchronous with speed buffering. Allows fixed DTE-DCE speed so
applications do not need to change the communications rate based on
connection results.