Hybrid routing is the routing of telephone calls in which numbering plans and routing tables are used to permit the colocation, in the same area code, of switches using a deterministic routing scheme with switches using a non-deterministic routing scheme, such as flood search routing.
Note: Routing tables are constructed with no duplicate numbers, so that direct distance dialing service can be provided to all network subscribers. This may require the use of 10-digit telephone numbers.
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".
References
Hybrid routing Wikipedia(Text) CC BY-SA