| 摘要 |
Apparatus and methods for determining an operational mode of a far-end modem are disclosed. Where the multimode modem is a call initiator, a method according to the invention includes transmitting a V.8 ANSam tone to the far-end modem, receiving a response signal from the far-end modem, and determining from the response signal whether the far-end modem is a commercial modem or a secure modem. Where the multimode modem is a call responder, a method according to the invention includes transmitting to the far-end modem a P1800 Hz tone with phase reversals, receiving a response signal from the far-end modem, and determining from the response signal whether the far-end modem is a commercial modem or a secure modem.
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