For ground start trunks, circuit pack or media module port relays are operated and checked to see if the port can detect and apply ground on the Tip lead. This test also verifies that there is no external ground on the Ring lead. In the absence of other failures, the media module should be replaced only if this test fails with the CO line disconnected.

This test also checks the on-board programmable transmission circuits that allow the media module to support transmission characteristics of several different countries.

This test runs on CO-TRK (Analog CO Trunk).