That has nothing to do with squelch tail.
" In continuous tone coded squelch systems as used in land mobile communications, for example, provision is made for eliminating the squelch tail by the use of the selective calling circuitry. In one type of continuous tone coded squelch system commonly used, the communicating transmitter sends a subaudible tone of one phase while transmitting a message and the same tone but of reverse phase for 150 milliseconds after the message; The receiver which includes a tone sensitive device such as a resonant reed, for example, in'response to the tone transmitted with themessage causes unsquelching of the receiver. The receiver therefore only receives when its particular tone. is transmitted and received. The reversed phase tone following the message damps the reed and results in the squelching of the receiver. This damping and resquelching of the receiver occurs rapidly and provides for the elimination of the squelch tail which would otherwise occur if only noise squelch were employed. For a further discussion of this type of system see Peth U.S.' Pat. No. 2,974,221. In other systems, the squelch tail elimination is-accom-' plished by. merely continuing carrier transmission for 150 milliseconds after the message without any reverse phase tone "
US3810023A - Automatic squelch tail eliminator for tone coded squelch systems - Google Patents
A squelch tail eliminator for use in a receiver having a continuous tone coded squelch system and provision for the disabling of the tone coded squelch system is disclosed. A pulse generator, responsive to the discontinuance of a given tone, generates a gating pulse that inhibits the disabling...
patents.google.com
" In continuous tone coded squelch systems as used in land mobile communications, for example, provision is made for eliminating the squelch tail by the use of the selective calling circuitry. In one type of continuous tone coded squelch system commonly used, the communicating transmitter sends a subaudible tone of one phase while transmitting a message and the same tone but of reverse phase for 150 milliseconds after the message; The receiver which includes a tone sensitive device such as a resonant reed, for example, in'response to the tone transmitted with themessage causes unsquelching of the receiver. The receiver therefore only receives when its particular tone. is transmitted and received. The reversed phase tone following the message damps the reed and results in the squelching of the receiver. This damping and resquelching of the receiver occurs rapidly and provides for the elimination of the squelch tail which would otherwise occur if only noise squelch were employed. For a further discussion of this type of system see Peth U.S.' Pat. No. 2,974,221. In other systems, the squelch tail elimination is-accom-' plished by. merely continuing carrier transmission for 150 milliseconds after the message without any reverse phase tone "
