Zhone Technologies, Inc. | IMACS Product Book, Version 4 |
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4. OCU-DP Card
The OCU-DP (Office Channel Unit - Data Port) is used to interface directly to DSU/CSUs (Data Service Units Channels Service Units) supporting data traffic up to and including 64Kbps. A four-wire circuit can connect the OCU-DP card to a DSU/CSU that can be located up to four miles away. In switched 56 Kbps mode, users can access the network on an as-needed basis by dial-up commands. The system unit must be equipped to provide -48 VDC power to fully support the functionality of the OCU-DP card.
OCU-DP Card Models
The IMACS supports three cards for support of external CSU/DSUs:
•8249 OCU-DP 2 Port Card
•824160 OCU-DP 5 Port Card
•824660 OCU-DP 10 Port Card
The 8249 OCU-DP card supports two ports while the 824160 and 824660 are five and ten port cards, respectively. All OCU-DP cards support RJ48 female connectors.
Each OCU-DP port can be independently programmed to operate at 2.4, 4.8, 9.6, 19.2, 56 and 64 Kbps in either DSO-A, (one channel per DS0) or DS0-B format, which allows multiple data ports from multiple OCU-DP cards in the system to be mapped into the same DS0 time slot. If the DS0-B format is selected, the user then specifies the type of DS0-B format required (b-5, b-10 or b-20) and the sub-rate position that the data port occupied by the data port within the DS0-B frame.
In switched-56K mode, an OCU-DP port provides a connection for an external Switched-56K DSU/CSU that will perform all call set-up and dialing functions. The OCU-DP card converts the call set-up commands into standard signaling and sends the signaling over the WAN facility.
All OCU-DP cards support a low speed secondary channel that is established in the 8th bit position of the DS0 time slot to which the OCU-DP port is assigned. The secondary channel can be used for testing and maintenance of the main circuit or for the transmission of other, independent, low speed data. The specification table shows the secondary channel rates associated with the standard primary port rates of the OCU-DP card.
The 8249 OCU-DP card also supports two methods of error correction. The first is known as “Majority Vote” and applies to the lower data rates, specifically, 2.4, 4.8 and 9.6 Kbps. The other is known as the BCH (Bose- Chaudhuri-Hocquenghem) method and applies to data rates of 19.2 Kbps and 56 Kbps. In the case of a 19.2 Kbps circuit, the error correction information is placed in the same DS0 that the circuit occupies. In the case of a 56 Kbps circuit, the error correction information is placed in a following, adjacent DS0 time slot on the WAN aggregate.
On all OCU-DP cards, performance statistics are collected by the system and are available through the user interface. Performance statistics include Errored Seconds (any second with an error), Severely Errored Seconds (any second with an error rate exceeding 10E-3) and Consecutive Severely Errored Seconds (CSES). They are displayed in one-hour intervals for up to 24 hours. CSES are counted by the system once ten consecutive Severely Errored Seconds are logged. The counter stops when the system logs ten consecutive non-Severely Errored Seconds. An OCU-DP port on the 8249 card may be programmed for OCU mode or CSU mode. OCU mode is the most common and is used whenever the OCU-DP port attaches to a CSU/DSU over a four-wire circuit. CSU mode allows the card to be connected directly to the digital network.
Software initiated diagnostics supported by the OCU-DP card include the setting of six different loop backs. Three of these act on the OCU-DP card itself and are known as local loop backs and the other three generate loop back patterns to remote devices and are known as remote loop backs. Among local loop backs, there are three types:
•Loop backs of the 4-wire analog interface of the OCU-DP port towards the attached CSU
•Loop backs of the 4-wire OCU-DP interface towards the network
•Loop backs towards the network at the point where the OCU-DP card interfaces with the system bus
