The following requirements apply to the external interfaces on the CO trunk side:

• The tip and ring default input impedance is 600 Ohms. The default impedance can be configured to accommodate other tip and ring impedances. One such impedance is the 900 Ohms that is used in Brazil. Another is the complex impedance that is used in the European Union.

• A hard-wired ground wire is added for each IROB-to-earth ground.

• The MM714 supports DTMF, MF, and pulsing.

• The MM714 supports R2MFC address signaling.

• The acceptable loop range for the CO trunk is 18 to 60 mA.

• The MM714 supports direct inward and outward dialing (DIOD) for Japan.