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Software engineering | Программная инженерия

Lesson 4

Read the text:  Background of the invention

In a telecommunications environment, such as in a telephone central office, customer expectations of superior service assurance dictate high levels of equipment availability and reliability. The expense of providing highly reliable central office computer-based equipment is justified because such expense is shared over a large number of customers.

One aspect of typical telecommunications equipment which improves overall system availability is "hot swap" or live insertion capability. "Hot swap" capability refers to the ability to replace failed circuit boards without powering down a whole system. Several hot swap schemes are known which employ electro-mechanical means to allow circuit board insertion and extraction. Such schemes typically use different length pins to control power connection and disconnection and circuitry to connect and disconnect output drivers from control and signal buses. One scheme employs a reset signal via a button to place a selected circuit board in a passive state during circuit board extraction. Another system uses a live insertion module coupled between a communication bus and a circuit board to provide complete isolation during power up/down sequences. A removal switch attached to the module activates power down of the module to allow circuit board removal.

With the explosion of new services in the telecommunications market, PC-based systems have migrated into the central office environment as adjunct systems for meeting some of these service needs. However, standard PC-based systems typically do not meet the availability requirements of the telecommunications environment. Modifications to improve the reliability of PC-based systems include adding redundant power supplies and disk drives. Nevertheless, typical systems have to be shut down in order to replace a failed circuit board. This down time is unacceptable in a telephone central office environment.

One common PC-based adjunct system modified for a telecommunications environment involves the addition of application-driven communication buses such as the Multi-Vendor Integration Protocol.RTM. (MVIP) communication bus.(H-MVIP Working Document, GO-MVIP, Inc., April 1995; Multi-Vendor Integration Protocol Reference Manual Release 1.0, Natural MicroSystems Corporation, 1991.) MVIP supports the integration of technology from diverse vendors and the integration of telephony functions and computing capacity by providing standard elements or protocols. These include a digital telephony bus, a telephone switching capability and the software conventions needed for an integrated system. The MVIP communication bus is typically implemented as a single ribbon cable which passes signals from circuit board to circuit board in a PC chassis.

Any hot swap of circuit boards configured with an MVIP ribbon bus are mechanically constrained by the ribbon cable. This can be seen in the configuration shown in FIG. 1. In this prior art circuit board configuration, circuit boards 10 connect to a backplane 12 by means of connectors 14. The backplane 12 may be in a standard PC chassis (not shown) and includes a communication bus, such as an Industry Standard Architecture (ISA) bus 16. A ribbon cable 18 is connected between circuit boards 10 via data bus connectors 20 and forms a communication bus such as an MVIP-compatible bus. Specifically, referring to FIG. 1, removal of any circuit board in this configuration is impeded by the presence of the ribbon cable 18. In addition, disconnecting the ribbon bus cable from the particular circuit board to be removed is likely to disrupt communications between other circuit boards connected via the bus.

                           1. Match the left part with the right:

2. Complete the sentences with the suggested words: sequences, circuit, module, insertion

Another system uses a live _______module coupled between a communication bus and a _______board to provide complete isolation during power up/down _______. A removal switch attached to the _______activates power down of the module to allow circuit board removal.