555定时器（时基电路）是一种用途广泛的模拟数字混合集成电路。1972年由西格尼蒂克斯公司（Signetics）研制；设计新颖、构思奇巧，备受电子专业设计人员和电子爱好者青睐；它可以构成单稳态触发器、多谐振荡器、施密特触发器和压控振荡器等多种应用电路。5

55定时器是一种中规模集成电路，它使用灵活、方便，被广泛应用于脉冲的产生、整形、定时和延迟等电路中。文中介绍了555定时器及其逻辑功能，以及由其构成的多谐振荡器的工作原理，通过举例论述了555多谐振荡器在模拟救护车声响电路中的应用，说明在实际生产中，只要将其各个功能加以综合应用，便可得到许多实用电路。

-555 timer (time base circuit) is a versatile analog-digital hybrid integrated circuit. Trinity Lakes in 1972 by Sigma Corporation (Signetics) development　layout and design, the idea of Kit Kat, much electronics design professionals and electronic enthusiasts favor　it can constitute a monostable, multivibrator, Schmitt Triggers, and a variety of applications such as voltage-controlled oscillator circuit. 5

Timer 55 is a medium scale integrated circuit, which uses a flexible, convenient, and is widely used in pulse generation, shaping, timing and delay circuits. This paper introduces the 555 timer and logic functions, and its composition multivibrator works, discussed through the example of 555 ambulances multivibrator sound in analog circuit applications, showing in the actual production, as long as Will be integrated application of its various functions can be many practical circuits.