TOPIC ---------------------------------------------
A user with an AppleFax Modem is having trouble receiving Faxes from
another Fax machine (the Hitachi DEX 6000). He has the new ROMs and is
running System 6.0.2 and AppleFax 1.2 software on a Macintosh II.
A Hitachi technical representative told him that our modem was responding
with an "RTP", not the expected "MCF".
He says that when the DEX initiates the call, it waits a moment and then
tells him there was an error in communicating. On the Macintosh side, the
AppleFax Modem answers the call and seems to be receiving the Fax, but when
he prints it, he just gets garbage.
DISCUSSION ---------------------------------------------
The "RTP" response sent by the AppleFax Modem is a request for retraining.
The modem sends this request when the data sent by the calling Fax machine
is corrupted during transmission. Phone line noise is one of the most
common causes. The "RTP" response is a valid response according to the T.30
specification (the standard for Fax machine communications).
The "MCF" response expected by the DEX 6000 is a message confirmation
response. This response is sent if the AppleFax Modem receives clean data
from the phone line.
It appears that the DEX 6000 is sending a packet of information that is
being corrupted by the phone lines. In response to the corrupted data, the
AppleFax Modem is sending a request for retraining, which seems to be
ignored by the DEX 6000. The AppleFax Modem continues to wait for the
retraining that it has requested. The DEX 6000 apparently does not
understand the "RTP" message, considers it an invalid response, and returns
an error code to the DEX user.