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Manufacturer: Zero One Networking
Model: ZyXEL U-1496
Latest Firmware Revision Tried: V 6.13 M
Recommended Firmware Revisions: V 6.13 M or V 6.12 M
Last Updated:$Date: 1995/02/20 01:16:11 $


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Includes support for digitized voice.

The first modem with working Class 2.0 support.

This modem is recommended for use with HylaFAX only with firmware revision 6.13 or later.

Most of the problems/issues listed here are fixed in the rev 6.13 firmware.

• AT+FMDL? and AT+FREV? return the same string, the concatentation of the modem model and the firmware revision.
• Some prom revisions do not include a trailing "OK" in response to AT+FDCC=?
• DC2 must be sent to the modem to trigger the transfer of Phase C data from the modem to the host after a AT+FDR command; this reflects revision 2388-B of the Class 2 spec and is different from the DC1 required by 2388-A (and accepted by most modems)
• The modem advertises that it supports the 2DMR data format, but it does not; this "advertisement" is both in its result string for a AT+FDCC=? query and in the DIS/DCS sent to clients
• Sending 2DMR data to the modem can cause it to lock up leaving CTS low to the host; some versions of firmware also send an infinite stream of trash to the remote side when this condition occurs
• In some prom revisions the result string from a AT+FDCC=? query does not conform to any syntax listed in either 2388-B or 2388-A; furthermore, it requires a context sensitive parser!
• AT+FDIS commands to set session parameters after establishing a connection with a remote machine are accepted but ignored; this makes it impossible to select/change data format (1D vs 2D encoding) and vertical resolution (98lpi vs 196lpi); since it is not in general feasible to set all session parameters before dialing the telephone, this problem makes it possible only to support the minimum set of Group 3 capabilities (1D data, 98 lpi)
• Sending non-Class 2 commands to the modem after establishing a connection often causes the modem to drop carrier; for example, ATM0 before a AT+FDR command will do this;
• The line counts in the +FPTS result code during a reception are total nonsense; the only way to deduce the number of lines in a received page of data is to parse the data on the host
• In later versions (5.05 for example) the syntax of the +FPTS: result code violates 2388-A and/or 2388-B
• There is no way to abort a session (i.e. the AT+FK command is not recognized)
• When sending, the modem appears to immediately drop DCD when it loses carrier; this usually occurs after a final AT+FPTS is sent to the host, but before the requisite OK and and/or +FHNG strings; this action appears to be independent of whether or not DCD is configured to follow carrier (i.e. &C0 or &C1)
• When receiving with a negotiated 14400 signalling rate, the +FDCS: status string indicates a 9600 baud signalling rate (br=3)
• The reception of multiple documents appears to cause the modem to hangup (i.e. an EOM post page message causes the modem to hangup)
• The modem sometimes sends received data to the host with the wrong bit order
• The scheme used to do adaptive-answer asserts a data carrier before falling back to a fax carrier; this can confuse a few fax modems and make it impossible to receive facsimile without disabling adaptive answer (AT+FAA=0)
• AT+FLID? returns "OK" but not the current value of the local identifier.
• The modem sends the host ^S/^Q during page data transmission (AT+FDT) even when RTS/CTS flow control is enabled

• When transmitting, it is not necessary to send RTC, the modem will append RTC to the page data upon receiving the post-page message from the host.

AT&T Paradyne DataPort