PU3 Module SWT 3000 Equipment Manual
Page - 16 Edition p3_3_2x 08/09 © SIEMENS AG 2008
Line interface G703.6 (2Mbit/s HDB3)
Coding in accordance with G.703.6 is also known as HDB3-code (High Density Bipolar of or-
der 3). Longer sequences of zeros, such as can occur with the AMI code are avoided here. If there
are four consecutive binary zeros the fourth character is changed by infringement of the AMI cod-
ing regulation. This means that a maximum of three consecutive binary values of "0" can occur with
the HDB3 code. The polarity of the changed code elements alternates. The HDB3 code is one of
the voltage-free codes.
It is possible to choose between a balanced line (120 ohm) and an un-
balanced line (75 ohm, connected to GND potential). The line imped-
ances are set with links.
Characteristics:
a) Balanced line
Number of signal lines: 4 (one balanced pair each for transmit and receive direction)
Level, transmitter end: "Space" 0V+/- 0,1V, "Mark" 1V
Level, receiver end: Loss at 1.024kHz 0...6dB
Impedance: 120 ohm
b) Unbalanced line
Number of signal lines: 4 (one unbalanced line each for transmit and receive direction)
Level, transmitter end: "Space" 0V+/- 0.237V, "Mark" 2.37V
Level, receiver end: Loss at 1.024kHz 0...6dB
Impedance: 75 ohm
Line lengths: short = indoor, long = outdoor
Bit rate: 2Mbit/s
Coding: HDB3
Jumper settings
All necessary jumper settings are shown in the chapter 2 “Installation and commissioning”. They
are also available in the SWTStraps program which is automatically installed with the PowerSys
service program.
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