These are the sounds of Mexico Standardized Telephone Tones. It is a pack of standardized telephone tones used in the United Mexican States. To avoid clicking sound at the beginning and in the end, the rising and falling times of the envelope of each tone burst are set to 5ms, which is the maximum allowed length for a telephone tone. Most of the sounds are loopable, except for continuous tones. If you need a longer sound you can send a request through the contact form or do precise cuts on the waveform and then loop the file. An alternative frequency may be used on some exchanges, that is why different versions have been included.
