It is necessary to consider the system testability problems for electronic devices during their early design phase because modern electronic devices become smaller and more compositive while their function and structure are more complex. Multisignal model, combining advantage of structure model and dependency model, is used to describe the fault dependency relationship for the complex electronic devices, and the main testability indexes (including optimal test program, fault detection rate, fault isolation rate, etc.) to evaluate testability and corresponding algorithms are given. The system testability analysis process is illustrated for USB-GPIB interface circuit with TEAMS toolbox. The experiment results show that the modelling method is simple, the computation speed is rapid and this method has important significance to improve diagnostic capability for complex electronic devices.

As an effective method for congestion control, active queue management plays an important role in improving the QoS of the Internet. In this paper, a newly developed TCP protocol Vegas and AQM are analyzed by dual theory. The mathematic model gives a better understanding about networks control, pointing out Vegas adapts to high speed network well and REM algorithm helps to achieve both high utility and low queue length. Simulation shows that REM is efferent, stable and outperforms current algorithms.

Through standard I/O interface, VISA can be the communication channel between zero-slot controller module and instrument. It is the kernel to make virtual instrument system open and interchange. While studying on the VPP specification in deeply, this paper discuss the design method of VISA resource template and node template, resource manager, I/O function, event handling, resource lock and etc. The applying results show this method has good property in system reliability and transplantable.

This paper describe a object orientied model of test systems by means of the disscusion of the limitation of the model based on function. There are several class in this model, i.e, mesured object, instrument including signal source & acqisition, reference standard,human observer and operation enviroment. It focus on the real-world aspect of a test system and provides a better model of the problem space. the model has the better consistency. The limitation and the application example of this model are also discused in this paper.