Product Versions
White modem, from 1980’s based design
Black Internal Modem, Homeworx
External Modem, 1 Ethernet Jack
External Modem, 2 Ethernet Jacks
HW Revision A: - First black case modem
HW Revision B: - "Volume Production" of perhaps 750-1000 units for shipment to 8-10 cable operators.
HW Revision C: - introduced a two board model and 4" tall case that would allow use with a traditional Ethernet 10BaseT connection instead of internal PC card. The external models used an RJ-14 style phone jack for serial control, configuration, and management using a Zenith supplied utility application.
HW Revision D: - Eliminated the susceptibility to RF interference from nearby cell phones. The fault would cause the transmit side Phased Locked Loop (PLL) to fail. Resolution required a power cycle, fault was non-detectable in software other than no connectivity.
HW Revision E: - Introduced dual 10BaseT interface for University of California San Diego, and other customers. Added modem MAC address to external CM, and in a barcode readable format.
All Zenith modems contained a small switch controlling the second coax port. The modem could either operate on one coax (built in diplex filter) or two (Headend use, dual plant networks, or external diplex filter.)
The initial Zenith "Headend" design was to use a residential cable modem inside a server, and a frequency translator to convert the upstream transmit frequency to the downstream receive frequency.
Clearly this design does not scale to more than a few networks, so the Channelmizer was introduced—a 2.5" tall rack mountable device with separate US and DS RF ports, the diplex filter switch, and an Ethernet port.
The first large scale Zenith headend was constructed in Cox San Diego using Zenith's booth demonstration hardware from the 1994 Western Cable Show. 3 Frequency Translators, plus 4 Channelmizers were loaded into a car and driven to El Cajon for installation Christmas Eve. These plus 3 other Channelmizers were interconnected to an 8 port Cisco Catalyst 1200 Ethernet switch with single mode FDDI uplink for a 4 device, 140 km FDDI ring around San Diego county. The Prodigy server obtained a traditional Ethernet card.
The 7 frequency translators + 7 Channelmizers supported 65,000 homes passed on 23 fiber nodes, and occupied a full rack.
Read more about this topic: Zenith Cable Modem
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