INTRODUCTION
3
1. 7 FCC Declaration
This equipment has been tested and found to comply with the limits for a Class A digital
device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference when the equipment is operated in a
commercial environment. This equipment generates, uses, and can radiate radio frequency
energy and, if not installed and used in accordance with the instruction manual, may cause
harmful interference to radiocommunications. Operation of this equipment in a residential
area is likely to cause harmful interference in which case the user will be required to correct
the interference at its own expense.
1. 8 Technical Overview
The DC3445 is used on unframed E3/G.703, or unframed DS3/G.703 digital services.
The product conforms with Directive 1999/5/EC (RE & TTE Directive). It also conforms with
the following Common Technical Regulations: 72/23/EEC (Low Voltage Directive),
89/336/EEC (EMC Directive) and EN 60950 (Safety).
1 . 8. 1 Signal Transmission
The signal is transmitted on 75 Ohm unbalanced coax. The signal has alternate mark
inversion (AMI) characteristics in accordance with G.703. A mark is transmitted as a 0
⋅
5 unit
interval (UI) wide pulse of amplitude 2
.
37V (75 ohm). Alternate marks have opposing polarity
so that '111' is transmitted as a positive pulse, a negative one and then another positive one.
The pulses have a duration of 50% so that strings of '1s' can be identified as a series of
pulses. This is because clocking information is derived from the transmitted signal. In
addition, strings of zeros are replaced with high-density binary 3 (HDB3) code words to
ensure pulse density (and therefore clocking information) and an average DC potential of 0V.
The transmission rate is 34.368 Mbps for E3, and 44.736 Mbps for DS3 connections.
The worst case delay through the DC3445 is 2 milliseconds, and the worst case round trip
delay is 8 milliseconds.
