## 1 Introduction
Many interesting solutions of two-port interconnections have been presented as parts of various fractional-order controllers [10; 11; 12; 13; 14; 15; 16; 17; 18]. Many of them are using standard topologies based on OA [10; 11] because of their simplicity. Some approaches target on extensive and complex design, based on field programmable analog arrays (FPAAs) [12] and field programmable gate arrays (FPGAs) [16; 17] because of their programmability. Moreover, FPGA represents a digital-only solution of the design. It allows the integration of highly complex topologies [12; 16; 17], but certain latency and delay of processing may occur in some cases. However, a significant drawback of these concepts is the necessity of software development and also quite high costs in comparison to a simple analog solution. Special analog active devices (with controllable internal parameters) used in the synthesis of controllers bring certain advantages in the simplification of the design and possibility of electronic adjustability/reconfigurability at the same time [13; 14; 15]. So-called bilinear synthesis brought significant contributions to the adjustability of the features of fractional-order devices [8; 18; 19; 20; 21]. Electronic tuning of zero and pole frequencies allows one to form an almost arbitrary frequency response with very simple and immediate reconfiguration [8; 19; 20; 21]. Analysis of known solutions leads to the following conclusions:  
1. Many proposed circuitries (except FPAA, FPGA-based) have quite complex topology, with many active and/or passive elements [9; 12; 16; 17; 18; 19], especially circuits with fractional-order behavior and approximations by higher-order filters [3; 5; 6; 13] or chain of bilinear segments [8; 9; 14; 15; 18; 19; 20; 21],
2. some concepts require software programming [12; 16; 17],
3. tested operational bandwidth is quite narrow in many cases [3; 4; 5; 7; 8; 11; 12; 13; 18],
4. summing of fractional-order as well as integer-order two ports was not analyzed deeply in the past,
5. single-parameter electronic adjustment of the time constant of the resulting response of two-port summing was not studied in the past, except [PERSON]. [PERSON] et al. [9], but the overall circuit topology is based upon a chain of bilinear sections, and therefore, it is not one of the simplest solutions  
Despite the presence of various solutions of the above-mentioned two-ports, the effects of their mutual interconnections are studied rarely [4; 8]. The most known cases of integral and derivative responses used simultaneously can be found in the field of controllers [7; 10; 11; 12; 13; 14; 15; 18]. However, a detailed study of resulting responses is often omitted. The first work ([PERSON] et al. [22]), where various simple interconnections of fractional-order devices has been studied, targets on combinations of two-ports. This work gives the evaluation of the resulting impedance functions of serial/parallel interconnections of fractional-order capacitors (RC approximants), where each two-terminal is actually represented by an active solution allowing simple electronic configurability and also floating implementation. Experimental tests were performed for very low frequencies (<1 kHz). [PERSON] et al. [23] introduced work dealing with more complex interconnections of real solid-state, fractional-order two-terminals. However, despite further attempts in the synthesis of passive [24; 25] or active [26] two-terminals, there are no attempts studying both simple and complex interconnections of fractional-order and integer-order two-ports. Moreover, the area of theoretical knowledge of fractional-order systems significantly extends into practical industrial applications [27]. To the best of the authors' knowledge, a similar study targeting on interconnections of fractional and integer order two-ports has not been presented in literature. However, there are many particular cases that should be studied.