The Commodore 1600, also known as the “VICMODEM”, is Commodore’s very first modem (1982): It supports 300 baud duplex connections, and is connected to an existing telephone’s handset connector instead of the phone line. This kept the price down, but required the user to dial manually through the phone.
The Commodore 1670, also known as the “Modem/1200”, is Commodore’s first Hayes-compatible modem: It connects directly to the phone line and supports pulse and tone dialing for 1200 and 300 baud duplex connections. There were two revisions, the original 1670 and the “new” 1670, a.k.a. CR-1670. (The unit in this article is the later revision.)