Atari modem

Greetings, I picked up a rather interesting 8-bit Atari system a while back. It is an Atari 130XE with 1050 floppy drive and a modem. What makes this system interesting is that it has been designed to be more portable. The 130XE's power supply, 1050's power supply, and modem, are all in a grey sheetmetal box, and the 1050 is bolted to the top. There is a large carrying handle on the front of the box, two illuminated power switches, a large unused red lamp, and an LED that is connected to the modem. On the back of the box is the power cord connector, a 7-pin DIN socket for the 130XE's power connection, a 15-pin D connector, and an unused 9-pin D connector. The telephone cable feeds through the crack between the box's lid and its side, and the power connector for the drive is fed through a hole drilled in the back. 14 pins of the 15-pin connector are wired up inside, so it looks like the modem is supposed to connect to the "Expansion" connector on the back of the 130XE (14-pin edge connector). Of course, whatever cable connected the computer to the modem has been lost (it was a Salvation Army find, so I was extremely lucky to get the power cable and SIO cable). The major part on the modem board is an NEC D80C48C. The board has the Atari logo etched on it. There appears to be only 8 actual connections to the board. Does anyone know what kind of modem this is? And which contacts should be wired to which contacts on the Expansion port? Thanks.