an echo canceler disabling system is associated with a cellular data communications device , such as a modem , which is utilized to communicate digital data over a cellular network for the purpose of enhancing digital data communications over the network . the echo canceler disabling system is configured to disable voice echo cancelers brought on - line during digital data transmission after call startup in order to prevent disruption of digital data communications by the voice echo cancelers . to deactivate the voice echo cancelers , the echo canceler disabling system is configured to transmit a tone at approximately 2100 hz with 180 degree phase reversals to disable one or more echo cancelers brought on - line after the call startup . in architecture , the echo canceler disabling system includes a mechanism to detect a loss of signal synchronization , a mechanism to send an echo canceler disable tone , and a mechanism to send a retrain signal after the echo canceler disable tone is sent in order to reestablish signal synchronization .