4 - Electronic Dialing and Ringing Circuits

Abstract

This chapter discusses the components found in conventional telephones, and explains how each component can be replaced with equivalent integrated circuits. Electronics have made the mechanical rotary dial obsolete. Solid-state integrated circuits are available, which generate dial pulses or tones when a telephone number is entered by depressing keys on a keypad. Integrated circuit dialing, ringing, and speech functions can be combined to form a complete, solid-state telephone that can provide such features as multitone ringing, tone, or pulse dialing with memory and redial, and an active speech network free of bulky transformers or coils. Old electromechanical dialers have been replaced by integrated circuits. Electronic memories can retain one or more phone numbers so that the touch of only one key on a keypad sends the entire number down the line. Likewise, electronic ringers have replaced the bell to signal an incoming call. Single-tone and multitone electronic ringers are available.