Method and apparatus for transmitting signaling tones over a packet switched network

#The present invention relates generally to the field of tone signaling. More specifically, the present invention relates to the field of transmitting tone signals over a packet switched data network.

#Tone signaling techniques such as “Dual Tone Multi Frequency” (“DTMF”) signaling are known and have been in use with telephone networks for at least the past twenty years. The advent and expanded use of packet switched telephony has presented certain barriers to the use of tone signals. In certain situations, encoders used to encode human speech may alter the frequency composition of a tone to the extent that that tone is not recognized by the device to be signaled. In another case, an encoder may alter the tone such that the device to be signaled mistakes the tone for another or may mistake the tone for two or more tones.

#DTMF Relays have been introduced in order to overcome this problem. The DTMF Relay is composed of a DTMF tone Detector and a DTMF tone Generator. The Detector monitors the incoming audio signal and upon detection of a signaling tone produces a control signal instructing the Generator in the receiving station to produce the signaling tone. Unfortunately, the detection of a signaling tone is time consuming and the relay path is sometimes delayed with respect to the voice path such that the signaling tone is detected twice at the receiving station. This is known as double-digit detection. It has been suggested to mute the voice path after the signaling tone is detected, however due to the time intensive nature of the detection process the muting of the voice path is delayed and some residual DTMF signaling is carried by the voice path to the receiving station causing double-digit detection.

#The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

#FIG. 1 shows a block diagram of signaling tone transmission system according to the present invention;

#FIG. 2 shows a block diagram of a frequency estimator according to the present invention;

#It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

#In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

#Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing”, “computing”, “calculating”, “determining”, or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.