This thesis is focused on the microprocessor-controlled frequency filter project. The main goal of the thesis is to present basic terms and principles of frequency filters and active frequency filters for cascading synthesis. Furthermore, the work contains information on digital potentiometers. The thesis includes circuit simulations and a project of connecting with a printed circuit board. The last chapter contains the results of the measurements.

The work deals with design of transformation cells suitable for realization of higher orders frequency filters with possibility of cutoff frequency control. At first, there is a common description of frequency filters and active elements like current and voltage conveyors. Furthermore assumptions of cutoff frequency control are defined which result in a convenient characteristical equation. Phylosophy of synthetic elements DP , EP , DS , ES including a possibility of change of cutoff frequency is next in line. By exploitation of synthetic elements theory new circuit’s schemes of transformation cells are searched. The work continues with the choice of appropriate transformation cells for resulting circuit’s solutions of frequency filters with possibility of cutoff frequency control by using transfer coefficients of active elements or with help of passive elements. The work concludes with verification of its proper function based on a simulation executed in OrCAD and with practical implementation of choosen circuit’s solution.

Vocabulary is a crucial component for language acquisition and EFL lessons are often dictated by the usage of textbooks and workbooks. The current study therefore aims to investigate how effective textbooks are in helping learners acquire high, mid, and low-frequency words as well as to what degree high and mid-frequency words are repeated throughout the textbooks. Additionally, the study explores the types of exercises presented in the EFL teaching materials, with a particular focus on the extent to which they promote learners' active engagement and use of the vocabulary presented. The findings suggest that EFL teaching materials could benefit from more comprehensive and systematic approaches to vocabulary instruction, which emphasize the active use and recycling of high and mid-frequency words in meaningful contexts. The present study recommends that teaching materials and EFL teachers incorporate more varied and interactive exercises that promote learners’ active engagement and use of the target vocabulary. Additionally, the study uses corpus-based methods to investigate the frequency level of text bodies compiled from EFL textbooks targeting sixth-grade pupils in Sweden. Furthermore, the accompanying workbooks are examined to establish the types of exercises pupils are exposed to through their use. In addition, the study suggests that teachers using the included teaching materials should incorporate additional vocabulary exercises in their EFL instructions to promote the repetition of words found in the textbooks.