Design of 8-Channel Answer Control System Based on Medium and Small Scale Digital Integrated Circuits

Abstract

In competitive answering scenarios, the reliable and rapid determination of which contestant responds first is a critical requirement that demands robust hardware-level signal processing. This paper presents the design and implementation of an eight-channel digital answer control system constructed exclusively from medium- and small-scale digital integrated circuits, addressing the core functional requirements of multi-channel signal priority judgment, answer signal latching, and timed countdown display. The proposed hardware architecture is systematically organized into four principal modules: a priority encoding module, an RS latch module, a decoding and display module, and a timing module. Specifically, the 74LS148 eight-line-to-three-line priority encoder is employed to perform real-time priority encoding of the eight-channel answering signals, ensuring that the earliest valid input is accurately identified. A 74LS279 quad RS latch circuit is subsequently utilized to lock the winning channel signal and suppress all subsequent inputs, thereby achieving effective answer interlock functionality. For the timing subsystem, a 555 timer configured in astable mode operates in conjunction with a 74LS161 synchronous four-bit binary counter to construct a precise hardware-based countdown unit. The 74LS48 BCD-to-seven-segment decoder drives nixie tube displays to visually present both the winning channel number and the remaining time. The complete circuit successfully realizes priority answer identification, signal interlocking, timed countdown, and real-time status indication. Simulation results conclusively verify the correctness and reliability of the proposed circuit logic. Notably, the design relies solely on widely available general-purpose logic chips without any programmable controllers, offering a simple, cost-effective, and easily reproducible solution suitable for educational and small-scale competitive applications.