How must the T1 PRI circuitbe configured to support this capability?

Your PSTN carrier sends digits to your T1 PRI circuit in a digit-by-digit format. How must the T1 PRI circuitbe configured to support this capability?
A. The T1 PRI controller supports either en-bloc or digit-by-digit formats natively.
B. The serial interface that is associated with the T1 controller needs to include the isdn incoming- voicecommand.
C. The T1 controller needs to include the isdn overlap-receiving command.
D. The serial interface that is associated with the T1/E1 controller needs to include the isdn overlap-receiving command.