Solid State Ringing and Tone Equipment with Programmable Timing

The paper describes a new generation of electronic ringing and tone signal equipments. After presenting the block diagram the operation of the basic functional units is described, such as the ringing generator - a voltage regulated transistor inverter -, tone generators with stabilized RC oscillators, tone contacts, timing circuits based on PROM´s and digitalized supervision circuits. High reliability is achieved using load-sharing principle for double sets. The structure based on functional modules gives versatility for different requirements on different markets and for applications to other than L M Ericsson exchanges.