Abstract: Reliable access to audio and facsimile message storage and retrieval systems is accomplished by employing a listening procedure to differentiate voice message clients from fax clients and, upon identifying a fax client, performing an extended listening procedure to differentiate between a sending fax client and a retrieving fax client. During the listening procedure, the system generates a ring tone, immediately after connecting the call, comparable in duration to that normally expected by a caller during a typical call attempt, thereby rendering the listening procedure transparent to a human caller. The masked listening procedure allows detection of standard calling fax machine, polling fax machines and accommodates a blind polling procedure for use with fax machines not equipped for standard call in polling. Blind polling is accomplished by monitoring a fax receiver in the system for a called station tone (CED) or if a CED tone is missed by the system, detection of V.21/V.

Abstract: Disclosed is a divide-by-m counter for generating an ouptut clock signal having a fifty percent duty cycle from a higher frequency source clock signal having m cycles for each single cycle of the output clock signal and wherein m may be an odd or even integer number, the divide-by-m counter including a modulo binary counter for counting up to a predetermined number, circuitry for presetting the modulo binary counter by another predetermined number, counter clock selector for providing a counter clock signal to the modulo binary counter which, when m is odd, will be either an non-inverted source clock or an inverted source clock based upon the occurrence of either the HIGH or LOW intervals of the output clock, and interval defining circuitry for defining the beginning of such HIGH and LOW intervals of the output clock based upon the occurrence of a ripple carry pulse from the modulo binary counter.