Chapter 6. Configuration42 ISU 2x64 Dual Port ISDN Service Unit User Manual 61200051L1-1DThe first byte of each packet contains all ones (A = FF HEX), andthe second byte of each packet (the C byte) is either 13 HEX or 03HEX if not the final packet.V.25 SYNC BISYNC DialingTo set the Dial Options for V.25 BISYNC, choose 3=V.25 BISYNCfrom the front panel or the VT 100 terminal (see Figure 6-8 formenu tree). This setting allows for V.25 bis messages in byte syn-chronous format (BISYNC). V.25 bis specifies that the charactersshould be ASCII, 7 bits, and odd parity. This setting allows syn-chronous data terminal equipment which does not use HDLC tosupport serial inband dialing.V.25 HDLC FLAGTo set the Dial Options for V.25 HDLC FLAG, choose 4=V.25HDLC FLAG from the front panel or the VT 100 terminal (see Fig-ure 6-8 for menu tree). Configuring the ISU 2x64 for HDLCFLAG V.25 bis enables in-band dialing over a DTE interface usingstandard synchronous HDLC V.25 bis commands with 7E HEXidle.DisabledThis selection disables in-band dialing over the DTE interface.Setting Auto AnswerAuto answer is configured separately for both DTE#1 andDTE#2. Using the front panel, select the appropriate DTE witheither arrow key and press Enter. When using a VT 100 terminal,select the option number corresponding to the appropriate DTEand press Return.The ISU 2x64 can be configured to automatically answer in one ofthree ways: Disabled, Enabled, or Dump all calls.DisabledWhen Disabled is selected, the ISU 2x64 will not answer the call.The AT answer command (ATA) must be issued to the ISU 2x64for it to accept the incoming call or by selecting Answer Callfrom dial menu. The ringing call can be dumped by using the
