Zenith Cable Modem - History

History

The Zenith cable modem was originally developed for a mid-split cable network in the mid-1980s, and used an 8 bit full height PC/AT type card containing an Intel 80186 dedicated CPU, connected to an external WHITE box about 2"x12"x6". Other similar products were made by Ungermann-Bass under the 10BROAD36 standard, and Vitalink. UB had models supporting RS-232 and Ethernet outputs, as well as a remodulating frequency translator.

In late 1993, Zenith and Prodigy provided about 12 modified 500 Kbit "white modems" to Cox Communications in San Diego, CA USA —including two with IBM Microchannel support. These modified modems were intended to support the Prodigy Cable Modem trial begun on a 1500 homes passed fiber node in El Cajon, CA. The modification allowed subsplit operation, with a fixed upstream frequency, and the downstream at 74.75 MHz, within the 4 MHz space between analog channels 4 & 5.

The initial trial consisted of a Prodigy server in the El Cajon headend, connected via the Microchannel based cable modem to an Olsen Frequency Translator. This basic network supported one 1500 home passed fiber node, with 6 "subscribers" including one employee of Cox who was also the Headend Manager. One card was installed in rack mount PC in the Federal Headend, another in the El Cajon headend. 1500 high pass filters were installed to eliminate any ingress from the drops. Service was reasonably reliable, and a newspaper article appeared in the Los Angeles Times.

Zenith updated their white modems to a matte black case, adding the Homeworx name, and marketing to cable operators in the $350 price range for 250 units. The new design used the same size external case, added LEDs to indicate power/TX/RX/activity, and replaced the full sized 8 bit ISA card with a smaller 16 bit version. The new design dropped the onboard CPU. The modem connected to the card using a 15 pin D-shell connector—which exactly matched the PC's game connector. Both models were powered by the PC. The new modem was frequency agile, with a configuration utility that ran on the PC to set up US and DS frequencies. Fortunately, the option to configure the card's MAC address was dropped. Unfortunately, the card’s MAC address was not printed on the outside of the board, and thus was invisible once installed in the PC. Nor was the MAC address printed in a machine readable (barcode format). Cox added these to the CM prior to installation, and tracked the subscriber to modem MAC address in an Excel spreadsheet, as the MAC address contained too many digits to fit into any fields within the customer billing system.