SALES_DED_PRE=
  (DESCRIPTION=
     (LOAD_BALANCE=OFF)
     (FAILOVER=ON)
     (ADDRESS_LIST=
        (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524))
        (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524)))
     (CONNECT_DATA=
        (SERVICE_NAME=SALES.ORACLE.COM)
        (SERVER=DEDICATED)
        (INSTANCE_ROLE=PRIMARY)
        (FAILOVER_MODE=
            (BACKUP=SALES_DED_PRE_SECONDARY)
            (TYPE=SELECT)
            (METHOD=PRECONNECT)
            (RETRIES=180)
            (DELAY=5))))

SALES_DED_PRE_SECONDARY=
  (DESCRIPTION=
     (LOAD_BALANCE=OFF)
     (FAILOVER=ON)
     (ADDRESS_LIST=
          (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524))
          (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524)))
     (CONNECT_DATA=
          (SERVICE_NAME=SALES.ORACLE.COM)
     (SERVER=DEDICATED)
     (INSTANCE_ROLE=SECONDARY)
     (FAILOVER_MODE=
         (BACKUP=SALES_DED_PRE)
         (TYPE=SELECT)
         (METHOD=PRECONNECT)
         (RETRIES=48)
         (DELAY=900))))

-- LOCAL LISTENER:

The values of the LOCAL_LISTENER parameter can be resolved through the local tnsnames.ora files on Nodes 1 and 2, respectively:
listener_SALES_HOSTA=
    (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1421))

listener_SALES_HOSTB=
    (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1421))

ORACLE DOC LINK: 

http://download.oracle.com/docs/cd/B10501_01/rac.920/a96601/5config.htm