Specifications

AN93
Rev. 0.9 131
If the server refuses to grant a modem-on-hold request, the modem will use the +PMHT setting to determine what
to do. If +PMHT = 0, the modem will remain connected to the server. If +PMHT is set to a non-zero value, the
modems will disconnect. The Si2493 will indicate these conditions with the result code, “MHnack; Disconnecting…”
or “MHnack; Reconnecting…”.
Once modem-on-hold has been initiated, it may be necessary for the Si2493 to perform a hook-flash to indicate to
the central office the incoming call may be accepted. This is initiated with the AT+PMHF command. The Si2493 will
go on-hook for the time set in user register U4F and remain off-hook while on-hold. Usually, a second hook-flash
is necessary to reestablish a data connection with the remote modem.
The Si2493 will attempt to reestablish a data connection with the remote modem upon receipt of the ATO
command and will indicate the connection has been reestablished with the CONNECT message. If the modems fail
to renegotiate the connection, the Si2493 will send the NO CARRIER message.
Table 87. Possible Responses to PMHR Command from Remote Modem
<Value> Description
0
V.92 Modem-On-Hold Request Denied or
not available. The modem may initiate
another Modem-on-hold request later.
1 MOH with 10 second timeout Granted
2 MOH with 20 second timeout Granted
3 MOH with 30 second timeout Granted
4 MOH with 40 second timeout Granted
5 MOH with 1 minute timeout Granted
6 MOH with 2 minute timeout Granted
7 MOH with 3 minute timeout Granted
8 MOH with 4 minute timeout Granted
9 MOH with 6 minute timeout Granted
10 MOH with 8 minute timeout Granted
11 MOH with 12 minute timeout Granted
12 MOH with 16 minute timeout Granted
13 MOH with indefinite timeout Granted
14
MOH Request denied. Future requests will
also be denied during this session.