SOLVED
I recently configured a CPTONE modified for analog lines connected to CANTV through FXO interfaces. The solution has proved successful disconnect supervision for incoming calls to the router's FXO ports on a Cisco ISR2911-V.
STEP 1
voice class custom-cptone CANTV
dualtone busy
frequency 425
cadence 500 500
dualtone ringback
frequency 425
cadence 1000 4000
dualtone reorder
frequency 480 620
cadence 250 250
dualtone number-unobtainable
frequency 480 620
cadence 250 250
dualtone disconnect
frequency 425
cadence 500 500
dualtone out-of-service
frequency 950
cadence 330 330
STEP 2
voice-port 0/3/3
supervisory disconnect dualtone mid-call
supervisory custom-cptone CANTV
input gain 10
timeouts call-disconnect 1
timeouts wait-release 1
timing hookflash-out 50
Regards
Saludos
LC