Hi Calvin,

You are most correct :) Cisco Emergency Responder 2.0 is the only version that works with CCM 6.x. Have a look;

Cisco Emergency Responder 2.0 supports the most recent versions of Cisco Unified Communications Manager, including Cisco Unified Communications Manager 6.0 and Cisco Unified Communications Manager 4.3

http://www.cisco.com/en/US/products/sw/voicesw/ps842/products_qanda_item0900aecd805e69cf.shtml

Cisco Unified CallManager Support

Cisco Emergency Responder (Cisco ER) 1.3(2) supports Cisco Unified CallManager versions 4.3 and 5.1 in addition to the previously supported Cisco Unified CallManager versions 5.0, 4.2, 4.1, 4.0, and 3.

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Note When upgrading to Cisco ER 1.3(2) from a previous version of Cisco ER, you will be prompted to enter the Cisco Unified CallManager version you are running. Although Cisco ER 1.3(2) does support Cisco Unified CallManager 4.3, version 4.3 is not listed as one of the available versions. If you are running Cisco Unified CallManager 4.3, select version 4.2 when prompted by the installation wizard.

http://www.cisco.com/en/US/products/sw/voicesw/ps842/prod_release_note09186a008077aa78.html

Cisco ER 2.0 supports a variety of hardware and software components, as shown below

Cisco Unified Communications Manager

Cisco Unified CallManager 4.2

Cisco Unified CallManager 4.3

Cisco Unified Communications Manager 5.0

Cisco Unified Communications Manager 5.1

Cisco Unified Communications Manager 6.0

http://www.cisco.com/en/US/products/sw/voicesw/ps842/prod_release_note09186a00808b64cf.html#wp42078

Hope this helps!

Rob