Miscellaneous Projects » Ericsson RBS 6xxx

h1. DUG 20

This is the second-generation GSM Digital Unit for RBS 6xxx.  It combines the baseband processing and back-haul interface of up to 12 TRX, in 1..6 logical BTSs.

The DUG 20 is only compatible with the [[RUS]] and [[RRUS]] radio units, not with the older [[RUG]] units.

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h2. Technical data

* -48V DC supply power

* 70W maximal power consumption

* Size: 8U x 31mm x 250mm

* Weight: < 2kg

h2. Flash

There is a CF slot on the left this device and it holds a 256mbyte CF card.  The card contains a FAT filesystem with both the software as well as the configuration (IDB = Installatin DataBase).

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h2. Connections

h3. Front Haul

The DUG 20 has 6 SFP slots for the interface towards the radio units, labelled RI A..F

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This is where you connect your [[RUS]] or [[RRUS]], either via direct-attach cables (usual for RUS), or via SFP transceivers and optical fiber (usual for RRUS).

h3. Back-Haul interface

The back-haul interface is Classic T1/E1/J1 (ISDN) based.  The DUG has four T1/E1/J1 lines exposed as two RJ45 connectors ("ET A" and "ET B")

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Pinout:

|_.RJ45|_.Line|_.Signal|

|1|A|RX tip (+)|

|2|A|RX ring (-)|

|3|B|TX tip (+)|

|4|A|TX tip (+)|

|5|A|TX ring (-)|

|6|B|TX ring (-)|

|7|B|RX tip (+)|

|8|B|RX ring (-)|

Same pinout as a Digium card with 2 lines per port.

So a cross-over cable is needed to connect to it.

h3. ESB port

note that its a bit smaller than the sfp slots

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h3. LMT B, LMT A, EC, GPS

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h3. LMT A

LMT (Local Maintenance Terminal) A hosts a RS-232 port used for connecting to the DUG 20 from a PC running the OMT software.

|_.RJ45|_.DB-9 (female)|_.Signal|

|1|5|GND|

|2|3|TxD|

|3|2|RxD|

h3. LMT B

Site-LAN and LMT B

FIXME

h3. EC

"Enclosure Control".  A (likely) RS-485 based site-local bus between different parts, particularly any power supply / climate systems and the digital unit. Used for monitoring/alamrs in case of environmental failure.

h3. GPS

This port is meant for attaching an external GPS receiver.  The connector includes

* RS485/422 receiver for NMEA from the GPS

* RS485/422 transmitter for command to the GPS

* RS485/422 receiver for 1PPS signal from the GPS

* 12V power supply for the GPS

h3. -48V DC in

Connectory type is a https://www.te.com/usa-en/product-1982299-3.html with associated crimp contacts.

{{thumbnail(DUG20_01_DC_in_detail.jpg, size=400)}}

Telecom equipment such as the DUG 20 typically has a positive ground system also known as "negative" 48 Volt[1].

Be aware (beware!) of short circuits. The chassis of the DUG and any other ground terminal on any port is connected to the +48v terminal, If any other equipment with a negative ground system is connected to the same DC supply as the DUG, there will be voltage difference between the ground terminals (and chassis) of this equipment..

h3. Connector on the Back

This connector is not used during normal operation.  We assume it is for factory / service use only.

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h2. LEDs

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h2. Overview Pictures

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h3. Internal pictures

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h2. Spare Parts

* 4-port RJ45 assenmbly including LMT ports: Amphenol RJHSE538004

* RS232 transceiver of LMT A port: ST3232ECTR

fn1. https://www.poweringthenetwork.com/uncategorized/negative-48-volt-power-what-why-and-how/