Alternate routing for a telephone system

An alternate routing system for a plurality of telephone switching offices, said system comprising:

• at least one group of trunk lines connecting any one switching office in said system to any other switching office in said system;
• each said switching office including a first plurality of storage locations, a second plurality of storage locations, and a third plurality of storage locations;
• said first plurality of storage locations, at each said switching office, storing, as an addressed location for said second plurality of storage locations, an indication of the terminating office to which a call is directed;
• said second plurality of storage locations, at each said switching office, storing, as an addressed location for said third plurality of storage locations, an indication of the switching office most likely to be available as a tandeming office between the originating switching office and the terminating switching office;
• said third plurality of storage locations, at each said switching office, storing, as an address location for said first plurality of storage locations, an indication of the trunk lines to be used for accessing the switching office indicated as being the tandeming office by said second plurality of storage locations;
• and
• means for periodically updating the information stored in said second plurality of storage locations, concerning the switching office to be employed as a tandeming office.

An alternate routing method for a plurality of telephone switching offices interconnected in a system configuration wherein any two switching offices in said system are interconnected by at least one group of trunk lines, said method, at an originating switching office, comprising:

• storing, in a first addressable storage location, an address indicative of a terminating switching office;
• storing, in a second addressable storage location addressed by the contents of said first storage location, an address indicative of a tandeming switching office to be employed intermediate said originating and terminating switching offices;
• storing, in a third addressable storage location addressed by the contents of said second storage location, an address indicative of trunk lines to be employed in accessing said tandeming switching office;
• and
• periodically updating the information stored in said second addressable storage location.