Code Efficient Carrier Detect for a Bell 103 Equivalent Modem
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
A Bell 103 equivalent modem is implemented by a general-purpose signal processor card designed for the IBM Personal Computer family. Carrier detection is the function of a modem that determines if the audible energy present on a telephone line is of the proper frequency and amplitude characteristics of a Bell 103 modem on the opposite end of the telephone line. Figs. 1 and 2 depict a classical approach to the Bell 103 equivalent modem and the new design. The Bell 103 specifications define two modes of operation: Originate and Answer. These modes further define the frequencies used to denote binary 1 and 0 values. The table below gives these frequencies: (Image Omitted) The Carrier Detect function must detect both the 1's and 0's frequency for a given mode and strongly reject the 1's and 0's frequency for the opposite mode.