8-4 MTR3000 Wireline: Functional Theory Of Operation
8.3.1.3 DC Control Decoder
The DC Control Decoder uses a collection of optocouplers and diodes to detect the amplitude and
polarity of DC currents on the Wireline Tx pair. The optocouplers provide a set of logic signals to the
FPGA that are used when the Wireline board is configured for DC Remote Control operation.
8.3.1.4 Surge Protection
The MTR3000 Wireline board implements 3 stages of surge protection on its Wireline port. In the first
stage of protection, sidactors limit the instantaneous voltage at the beginning of a transient event by
shunting current between voltage potentials. In the second stage of protection, Positive Temperature
Coefficient (PTC) fuses disconnect the Wireline Tx and Rx paths from the base station/repeater
backplane interface board when the transient current exceeds specified levels. In the third stage of
protection, transient voltage suppression diodes will clamp line-to-line events that exceed 9V.
8.3.1.5 Impedance Matching Network
The impedance matching network is intended to present a known configurable impedance to
equipment connected at the far side of the Wireline cable. Line impedance is generally standardized
by country or region. The matching network uses 24 analog switches to switch resistors and
capacitors onto the receive and transmit audio paths. For any given impedance setting, 3 switches
are closed. On the receive pair, impedances are switched in series with each line and on the transmit
path impedances are switched in parallel. The line impedance setting is configured using the CPS
software configuration tool. The Wireline’s FPGA will close the correct switches based on the CPS
configuration setting.
Table 8-2 shows the line impedance supported by the Wireline board based on the country or region.
Note
The PTC fuses are designed to automatically reset when line conditions return to normal. All
surge protection components (including the PTC fuses) are not intended to be field
serviceable.
Table 8-2 Impedance supported by Wireline board
Option Functionality
High Impedance For use with an external impedance matching
600 Ω For Argentina, Canada, Chile, Columbia, Ecuador, El
Salvador, Guam, Hong Kong, India, Indonesia, Japan,
Jordan, Kazakhstan, Kuwait, Macao, Malaysia, Mexico,
Oman, Pakistan, Peru, Philippines, Russia, Saudi Ara-
bia, Singapore, South Korea, Taiwan, Thailand, UAE,
USA and Yemen
270 Ω + (150 nF || 750 Ω) For Austria, Belgium, Denmark, Finland, France, Ger-
many, Greece, Iceland, Ireland, Italy, Luxembourg,
Netherlands, Norway, Portugal, Spain, Sweden, Swit-
zerland, Bahrain, Croatia, Cyprus, Czech Republic,
Egypt, Hungary, Israel, Latvia, Lebanon, Malta,
Morocco, Nigeria, Poland, Romania, Slovakia and Slo-
venia
220 Ω + (115 nF || 820 Ω) For Australia, Bulgaria and South Africa
370 Ω + (310 nF || 620 Ω) For New Zealand
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