If the tone returned is detected as busy or the adapter detects ring back tone and the telephone does not answer after, in one example, three rings , {HEAD ~ the adapter} will hold {TAIL ~ the DID line} up to the Central Office or E&M tie line to the originating switch 
hold
If the tone returned is detected as busy or the adapter detects ring back tone and the telephone does not answer after , in one example , three rings , { HEAD ~ the adapter } will hold { TAIL ~ the DID line } up to the Central Office or E&M tie line to the originating switch
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