Issue:
The MP/8 or MP/16 modem-cards are a special rack-version of the 3COM/USR 'Courier V.Everything' modem-type. However the MP/x versions use an 8-pin 'RJ-45' connector for their EIA interface. A seperately purchased RJ-45 to DB-9 conversion cable is used for the connection to a Perle833 Port. Eight of the nine standard 'PC Serial Port' supported EIA signals are present at the DB-9 side. The ninth pin: 'Data Set Ready (DSR) - DB9-pin6' is not connected. The Perle833, however, requires an active signal on pin6-DSR to unconditionally indicate that a modem is attached and powered on. An inactive-to-active transition on pin6-DSR will cause the Perle833 native, port-specific, 'init-string' to be sent to the modem. An unconnected DB9-pin6 will indicate that the port is not available (out).

Solution:
Several solutions are possible. All methods centre around supplying a constant voltage level , ( >+3V) to each active Port's DB9-6 pin that has a modem attached: 

1. This hardware-only solution is probably the cleanest, once implemented. Modify the DB-9/RJ-45 terminated cables by supplying an active voltage level to DB9-pin6. A voltage between +3 and +12 volt will do the job. Worst case, with all eight ports connected at +12V, 20 milli-amp will be consumed. Preferrably, obtain the voltage from the MP/8 unit, this provides maximum flexibilty for all Perle833 ports. Alternatively, it is possible to use the DB9-pin4 (DTR) from a 'Dial-In Only' Perle833 port, to supply one or more DSR signals. However, do NOT use DTR from a port configured for dial-out as a DSR source, since Win9x/WinNT will drop DTR at inopportune times. 

2. This modem-firmware solution is technically the simplest, but requires a special version of the modem-firmware. According to USR's 'Version 2.1 (modem code) Release Notes', an additional 'S register - S58' was added to support the 'x2' protocol. The high-order bit of S58, when set, provides DSR instead of 'Ring Indicator (RI)' on RJ-45 Pin1, which connects to DB9-pin9. The Perle 833 ignores 'DB9-pin9 (RI)', hence we can safely remove DB9-pin9 and re-connect it to DB9-pin6. However, upon executing the standard '&F - Reset To Factory Defaults' sequence, S58 is cleared. A special/patched firmware version which sets the high-order bit of S58 upon '&F[x]' will correct this. 3Com/USR will need to supply the details for your modem firmware version. 

3. The software solution is more tedious, but does not require special firmware: 
* Modify the MP's modem-adapter cables, at the DB-9 end, as follows: Remove (RJ-45 Pin1 to) DB-9 Pin9 (RI) and add (RJ-45 Pin1 to) DB-9 pin6 (DSR). 
* Obtain the correct mdmxxx.inf file from 3Com/USR (in this case MDMCRV90.INF). Copy it to a floppy. 
* Edit this file by adding 'S58=128' to the 'HKR Init, 2,,.....' strings, as follows: HKR, Init, 2,, "AT&F&B1&C1&D2&M4&K1E0Q0V1&A3 S58=128 ". 
* Rename file to an appropriate 'MDMxxxxx.INF' name. Uninstall all previously installed Courier modems. Remove 'DRVDATA.BIN' and 'DRVIDX.BIN' files from WINDOWS\INF directory. 
* Install this new 'MDMxxxxx.INF' modem-type, via add new hardware/modems/have disk, on your dialout-port (normally Port5). 
* Add a 'Custom Modem' to the Perle833, by modifying via the Manager, the 'US Robotics Courier x2' init strings. Again, 'S58=128' will cause DSR to be selected. 
* Note that some Applications, such as WinFax8/9, identify their own '&F' init strings. Again the 'S58=128' then needs to be appended.