Voice message notification is optional and requires subscription to telephone company's voice messaging service (or subscription to another voice messaging service provider which has access to Phone Company's message waiting indication service).
ISDN Ordering Code for this configuration for a NI-1 ISDN line is Motorola Access 3 (or Capability Package P).
PowerFone works on National ISDN-1 & 2, Custom AT&T 5ESS
(Point-to-Point and Multipoint) and Custom DMS-100 ISDN lines.