50. A method of invoking a feature in a switching system having an internal numbering plan in a telecommunications network having a network numbering plan, comprising the steps of: receiving at the switching system a first symbol sequence included in the internal numbering plan; in response to receiving the first symbol sequence, parsing the received first symbol sequence by using stored first information defining the internal numbering plan and defining the first symbol sequence as a feature access code for a feature of the switching system, to determine a meaning of the first symbol sequence within the internal numbering plan; receiving at the switching system a second symbol sequence, different from the first symbol sequence, that is included in the network numbering plan and including an extension number of the switching system; in response to the receipt of the second symbol sequence, parsing the received second symbol sequence by using stored second information defining the network numbering plan and defining the second symbol sequence as a feature access code for said feature of the switching system, to determine a meaning of the second symbol sequence within the network numbering plan; and in response to the determined meaning of either one of the received first symbol sequence and the received second symbol sequence, invoking said feature in the switching system.
50. A method of invoking a feature in a switching system having an internal numbering plan in a telecommunications network having a network numbering plan, comprising the steps of: receiving at the switching system a first symbol sequence included in the internal numbering plan; in response to receiving the first symbol sequence, parsing the received first symbol sequence by using stored first information defining the internal numbering plan and defining the first symbol sequence as a feature access code for a feature of the switching system, to determine a meaning of the first symbol sequence within the internal numbering plan; receiving at the switching system a second symbol sequence, different from the first symbol sequence, that is included in the network numbering plan and including an extension number of the switching system; in response to the receipt of the second symbol sequence, parsing the received second symbol sequence by using stored second information defining the network numbering plan and defining the second symbol sequence as a feature access code for said feature of the switching system, to determine a meaning of the second symbol sequence within the network numbering plan; and in response to the determined meaning of either one of the received first symbol sequence and the received second symbol sequence, invoking said feature in the switching system. 52. The method of claim 50 wherein: the stored first information defines the first symbol sequence same as the stored second information defines the second symbol sequence; and the step of invoking comprises the steps of in response to the determined meaning of the received second symbol sequence, invoking the feature that corresponds to the second symbol sequence by using the determined meaning and the stored second information, and in response to the determined meaning of the received first symbol sequence, invoking same said feature by using the determined meaning and the stored first information.