Your PSTN carrier sends digits to your T1 PRI circuit in a digit-by-digit format. How must the T1
PRI circuit be 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 incomingvoice command.

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.

Explanation:
Configuring Overlap-receiving on the D-channel changes the way routers behave
when receiving ISDN calls. Overlap receiving allows the matching of dial peers as the digits are
being received. The router responds to the setup message with a SETUP ACK. This informs the
network that it is ready to receive further information messages containing additional call routing
elements.
http://www.cisco.com/en/US/tech/tk801/tk133/technologies_tech_note09186a00800b48cb.shtml