Multimode modem with automatic negotiation of operational mode
AssigneeL-3 Communications Corporation
InventorFrank A. Costantini
Life of this patent
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Abstract
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.
Claims20
A method for identifying a far-end modem type, comprising:
- transmitting a V.8 ANSam tone to the far-end modem;
- receiving a response signal from the far-end modem in response to the transmitted V.8 ANSam tone;
- and
- determining from the response signal whether the far-end modem is a commercial modem or a secure modem.
A method for determining a far-end modem type, comprising:
- transmitting to the far-end modem a P1800 Hz tone with phase reversals;
- receiving a response signal from the far-end modem in response to the transmitted P1800 Hz tone;
- and
- determining from the response signal whether the far-end modem is a commercial modem or a secure modem.
A method for determining a far-end modem type, comprising:
- monitoring an incoming channel for the presence of any of 1800 Hz energy or 2100 Hz energy;
- if 1800 Hz energy is present in the incoming channel for at least about one second, then determining that the far-end modem is a secure modem in half-duplex mode;
- and
- if 2100 Hz energy is present in the incoming channel for at least about one second, then determining whether the far-end modem is a V.32 modem or a secure modem in interoperable mode or alternate mode.
A computer-readable medium having stored thereon computer executable instructions for performing a method for identifying a far-end modem type, comprising:
- transmitting a V.8 ANSam tone to the far-end modem;
- receiving a response signal from the far-end modem in response to the transmitted V.8 ANSam tone;
- and
- determining from the response signal whether the far-end modem is a commercial modem or a secure modem.
A computer-readable medium having stored thereon computer executable instructions for performing a method for identifying a far-end modem type, comprising:
- transmitting to the far-end modem a P1800 Hz tone with phase reversals;
- receiving a response signal from the far-end modem in response to the transmitted P1800 Hz tone;
- and
- determining from the response signal whether the far-end modem is a commercial modem or a secure modem.
Dependencies are inferred from the claim text.