Modular Ringing, Tone, Cadence Supplies for Electromechanical Switching Systems

The requirements of Ringing and Tone Plants for various Electromechanical Switching Systems in use in the North American Telephone Network are described. The commonalities and differences are identified, indicating that a Modular approach can be utilized to provide a cost effective replacement for the absolete Ringing and Tone Plants (mainly rotary types) supporting the Electromechanican Systems. The Modular approach resulted in the development of separate modules providing individual tones, ringing and cadence functions. These modules were later used to create a family of three Ringing and Tone Plants:- RT1 - to support North American Step-by-Step Systems RT2 - to support X-Bar Systems RT3 - to support British Post Office Step-by-Step Systems To guarantee highly reliable and uninterrupted service, each Ringing and Tone Plant consists of duplicated systems with three levels of monitoring and automatic transfer when a fault is detected. To eliminate unnecessary service calls for false alarms, the plants are equipped with `Remote Reset´ and `Remote Transfer´ features. Finally, the architecture of these three Ringing and Tone Plants is reviewed to demonstrate how three different Ringing and Tone Plants can be assembled from identical building blocks to provide a flexible and a cost effective solution to the varied requirements for ringing, tone and cadence functions of a great majority of Electromechanical Switching Systems.