5100 Modem as TDMA line card

Hi folks got asked a question the other day have been working with iDirect for a while now but wanted to see what everyone thought of this one

Question :

"can you use an infinity 5100 modem as a TDMA line card?? we have a chassis but no spare cards and this is only for a small network and dont want to buy a line card for three vessels!!""

What does everyone think???

Cheers