During the lifetime of the MAXen, there have been several enhancements in Rockwell´s modem-chip design and modem technology. Ascend did develop its first plugin modem card the MX-SL-8 modem with up to 33 kilobit.
This is a non S56 chip based card. Check the versions here.
On the used market, there are old used MX-SL-8-V34 and MX-SL-12 (Not S56) digital modem cards from Ascend for MAX 1800/2000/4000 - but not for MAX 6000 series routers. It is the older 33K model and not running 56 Kilobit !!!!!
But the MX-SL-12 is a pretty good and very reliable solution for any modem test and usage and/or a dial- out FAX Service (we dont know about dial-in) in an ISDN-S0 / E1 / T1 environment.
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Furthermore these cards are no more supported by the new TAOS releases higher then 7.0.4. Use it for tests or Fax purpose. These units have a really heavy steel case. The newer ones have a light alumnium case and the type III cards have no more a case at all (however).
And you cannot mix them with other S56 modem boards in the same unit !!
To avoid overheating problems in the MAX 4000, have a look at www.maxrepair.com . We suggest a maximum of two cards in a MAX 4000.
In our POP, a modem board runs very well in our dial-in MAX4000 and one in a test-MAX 1800. The newer modem boards inside a MAX 1800 have some kind of throughput (or speed) problems, we did never find out why.
The Rockwell chipset RC288DPL was used inside this older modem card.
The RC288 chip itself was placed on eight little paddle boards. To talk from and to the MAX mainbaord, there has been a need for some gate- and buffer- chips. These chips reside on the main board of the modem card.
