JPS55151885A - Digital signal discriminator - Google Patents

Abstract

PURPOSE:To secure formation of the digital filter group without using any multiplier, by providing properly the cam filter and the positive paired tap filters to make only the desired single frequency signal pass through these filters and then deciding the presence or absence of the signal thereafter. CONSTITUTION:Input signal IN sent from input terminal 10 is branched to receive the spectrum inversion via specturem inverter 2, and thus 2,600Hz and 2,400Hz are inverted to 1,400Hz and 1,600Hz each. Then the signal is branched, and the components of 1,400Hz and 1,600Hz are eliminated through band eliminating filter 3. The level detection is then given to the signal through level detector 41, and the signal is supplied to deciding logic circuit 5. On the other hand, the signals entered BPF31 and 32 are detected through level detectors 42 and 43 for presence or absence of the line signals of 1,400Hz and 1,600Hz each to be then supplied to circuit 5. And the signal branched directly through terminal 10 is decided for the presence or absence of the register signal through BPF groups 33-38, level detectors 44-49 and circuit 5 each. And this information is delivered to the exchange through terminal 20.