Which of the following is TRUE with regards to ISDN?

You work as a technician at ABC.com. ABC.com provides networking services to external clients.
One of ABC.coms clients has requested an ISDN configuration.

Which of the following is TRUE with regards to ISDN? (Choose all that apply.)

A.
ISDN can be used over the client�s existing telephone network.

B.
ISDN requires an upgrade to the client�s existing telephone network.

C.
ISDN is capable of communicating at speeds of up to 128 Kbps.

D.
ISDN is capable of communicating at speeds of up to 56 Kbps.