42 Chapter 4 CS 1000 considerationsNN40140-500NN40140-500c Ensure that the DN Type is Public (Unknown).d In the External Number field, enter the NPA-NXXX of the DID trunks that serve themain office.e Assign the PSTN line pool to the route (select the line pool from the Use Pool list; defaultis A).4 Add a destination code.a Access the Dialing Plan - Routing panel (Configuration > Telephony > Dialing Plan >Routing) and select the Destination Codes tab.b Add a new destination code.Use the ALTPrefix as the destination code.c On the ALTPrefix Destination Code row, select the Normal Route field.d Enter the route for the route added above (996).e In the adjacent Absorbed Length field, select 3 from the list.When the SRG receives the ALTPrefix+DN digits from the main office, it looks up the destinationcode table, finds a match for the ALTPrefix, dumps the 3- digit ALTPrefix, appends the DN to theExternal Number and dials the External Number+DN.Emergency Services Access (ESA) configurationThe Main Office Configuration for Survivable Remote Gateway 50 (NN43001-307) guide coversthe procedures for configuring Emergency Services Access on both the SRG and the CS 1000. Theinformation here expands on the SRG procedure in that guide.There are two methods of ESA support:• When a user dials 911, the telephone is redirected to the Branch Office and connects tothe SRG in local mode. The Main Office indicates the reason for redirection (as e911)in the DRAM. The SRG dials 911 across the PSTN. The telephone remains in localmode after the 911 call and is redirected to the Main Office after 10 minutes.• On-site notification for 911 — An external tool records an alarm when 911 calls aremade at the branch office. This is applicable to both telephones that are in local modedue to the activation of a 911 call as well as locally connected analog sets. Theexternal tool connects to the SRG through LAN CTE.Note: This procedure applies only to redirected IP telephones when theSRG is in normal mode.For IP telephones in local mode, and for other telephones at the SRG, seethe Networking Configuration Guide (NN40020-603) for configuringemergency services.