TNETEL1200

EtherLoop

™ MODEM

SPHS003D – FEBRUARY 1999 – REVISED JUNE 1999

2

POST OFFICE BOX 655303

description

The TNETEL1200 is an EtherLoop modem. EtherLoop technology enables simultaneous voice and Ethernet

communication over local-loop plain old telephone service (POTS) wiring. The TNETEL1200 supports data

rates of up to 6 Mbit/s and POTS wire lengths of up to 21,000 feet. Figure 1 shows a typical system with an

EtherLoop modem located at each end of the POTS line. Each EtherLoop modem has a 10Base-T Ethernet

interface and is responsible for buffering Ethernet data before sending it over the POTS wire. The server-end

(SE) EtherLoop modem is located in a central switching office and can communicate with several client-end

(CE) EtherLoop modems, based on a round-robin arbitration scheme. The CE EtherLoop modem typically is

located at a remote site.

POTS

Line

POTS

Line

SE Modem

Ethernet

Network

Central Office

CE Modem

CE Modem

Remote Location

Ethernet

Network

Ethernet

Network

¤

¤

See Note A

NOTE A: Flexible multiplexing scheme allows one SE modem to interface with many CE modems.

POTS Phone

POTS Phone

Remote Location

Figure 1. Typical EtherLoop System

Figure 2 shows a block diagram of a typical CE EtherLoop modem. Ethernet data destined for the POTS wire

is received via 10Base-T interface and presented to the EtherLoop processor. The EtherLoop processor

performs Ethernet frame processing and buffer management. The EtherLoop processor sends buffered

Ethernet frames to the TNETEL1200 EtherLoop modem (via an HDLC interface). The TNETEL1200 performs

data modulation before passing the modulated digital data to a digital-to-analog converter (DAC). The resulting

analog signal passes to the EtherLoop transceiver, which acts as the line interface. The modem uses a

half-duplex communication protocol over the POTS wire, and data received from the POTS wire follows the

reverse path back to the Ethernet framer.

Ethernet

Network

Ethernet

Interface

POTS

Line

EtherLoop

Processor

TNETEL1200

EtherLoop

Modem

DAC

ADC

POTS

Phone

EtherLoop

Transceiver

SRAM

Voice

Band

Filter

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Figure 2. Typical CE EtherLoop Modem