82 / Working with ISDNModular ICS 7.1 Installer Guide N0130943 02line 001, either line 001 or line 002 is selected. For loopswhich use a single SPID, assign both lines on a loop to atelephone to guarantee that all calls appear at thetelephone.Programming Direct Inward System Access (DISA) onPRI trunksWhen a trunk cartridge is set to PRI, all lines on that trunk areset to Auto Answer without Direct Inward System Access(DISA).DISA can be accessed by one of two methods.1) Define the DISA DN to match the trailing digits of theCalled Party Number (CDN).With Public, Private, and Tie service types, the CDN issimply truncated to the Target Line Receive Digit Lengthand is parsed to match the Target Line Receive Digits.DISA can be accessed by having the DISA DN match thetrailing digits of the CDN. For example, with a ReceiveDigit Length = 4, and DISA DN = 1234, a call made toPublic DN 763-1234 will be handled as follows:• the ISDN setup message will contain a CDN of 763-1234• the CDN will be truncated to the four digits, 1234• 1234 matches the DISA DN• the call will be answered with DISA2) Use incoming Call by Call (CbC) Service routing to map thecall type to the DISA DN. Refer to Programming Call byCall service selection on page 475 for more information.With FX, INWATS, 900, and SDS service types, either aService Id (SID) or a CDN is mapped to Target LineReceive Digits.
