ZyXEL Omni TA 128 User Guide - Page 74

is deemed as a bundle request. The two data calls are established following normal call control procedures. That is, the network treats them as two independent calls. Both TA's use X.75 Multiple Link Protocol or 'cFos' channel bundling protocol to coordinate the two B channels. The former would need an overhead of two octets for each packet. The success of bundle connection initiation is indicated by the connect message reported to DTE as follows: CONNECT 460800 / X.75M 128K / V42b If a B channel is unavailable at either site then the bundle initiation will fall back to single channel connection. In this case the connect message may be as follows: CONNECT 460800 / X.75 64000 / V42b Dialing Pre-stored Phone Numbers The 40 phone numbers stored in the NVRAM can also be used to place a bundle call: • Use ATDSn, - (n=0-39), to dial the (n+1)th phone number twice for both the bundle connections. • Use ATDSn+, - (n=0-38), to dial the (n+1)th phone number for the first connection and to dial the (n+2)th phone number for the second connection. • Use ATDSn+Sm, - (n=0-39; m=0-39), to dial the (n+1)th phone number for the first connection and the (m+1)th phone number for the second connection. Invoking V.42bis Data Compression The following AT commands are used to switch the V.42bis data compression on or off for ISDN data calls when using X.75 or V.120 protocols: • AT&K44 - (enable V.42bis on ISDN call) 62