25. A switching system having an internal numbering plan for use in a telecommunications network having a network numbering plan, comprising: means, responsive to receipt of a first symbol sequence that is included in the internal numbering plan, for interpreting the received first symbol sequence at the switching system to be a feature access code of a feature of the switching system, and further responsive to receipt of a second call-control symbol sequence, different from the first symbol sequence, that is included in the network numbering plan and that is assigned, within the network numbering plan, to an extension of the switching system, for interpreting the received second symbol sequence to be an equivalent of said feature access code of said feature of the switching system; and means responsive to the interpretation of either one of the first symbol sequence and the second symbol sequence, for invoking said feature in the switching system.
25. A switching system having an internal numbering plan for use in a telecommunications network having a network numbering plan, comprising: means, responsive to receipt of a first symbol sequence that is included in the internal numbering plan, for interpreting the received first symbol sequence at the switching system to be a feature access code of a feature of the switching system, and further responsive to receipt of a second call-control symbol sequence, different from the first symbol sequence, that is included in the network numbering plan and that is assigned, within the network numbering plan, to an extension of the switching system, for interpreting the received second symbol sequence to be an equivalent of said feature access code of said feature of the switching system; and means responsive to the interpretation of either one of the first symbol sequence and the second symbol sequence, for invoking said feature in the switching system. 31. The switching system of claim 25 wherein: the interpreting means include means for receiving the symbol sequence from a user directly served by the switching system.