Technical Reference for ZyXEL omni.net series 

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It takes about 2 seconds for the calling ISDN TA to send XID and wait until time out. If you know 

in advance that the called site has no V.42bis capability, it is advisable to issue the AT&K00 

command beforehand in order to get a quick connection. 

Although not defined in X.75, XID frame is based on the encoding in ISO Standard 8885 and is 

used in V.42/V.42bis. In addition to the compression parameters, XID can be used to negotiate the 

packet parameters for example as window size or packet size. 

Selecting V.120 for European ISDN (DSS1) 

With European ISDN, V.120 is an option in the Bearer Capability (BC) information element, which 

is a mandatory information element in the SETUP message. Although we can specify V.120 in the 

Low-Layer-Compatibility (LLC) information element, some switches just don't deliver the LLC. 

Other switches do deliver the LLC, but the V.120 selection will be discarded midway. 

If the called ISDN TA does not get any B-channel protocol information from the incoming SETUP 

message and the remote device is a ZyXEL ISDN device, the called ISDN TA will be able to 

identify the V.120 protocol automatically with the Multi Auto-answer routine. Otherwise, with 

other ISDN devices, the handshake will fail. 

Security Settings 

The omni.net LCD/Plus/D provides security functions used to prevent unauthorized connections. 

Your omni.net ISDN TA features two security types with three levels of checks for added 

flexibility in the device you are connecting to and the transmission protocols you are using. 

Two types of security functions are provided. 

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Type 1 Security

 is exclusively used when the remote device is ZyXEL ISDN TA. 

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Type 2 Security 

can be used with remote ISDN TAs of any brand (including ZyXEL ISDN 

TAs). 

With a Type 1 connection, the dial-in (remote) ZyXEL ISDN TA will send in its supervisor