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Musical doorbell built on microcircuit UMS8-08. Standard connection diagram Most of the doorbells made in Russia nowadays use the popular microcircuit-synthesizers of the UMS series. Now we are not surprised by the variety of sound effects produced as we press the button of a doorbell. The microcircuits of this series can play up to eight programmed melodies automatically. The UMS series microcircuits are ROM devices programmed so that in the information read mode the frequency of the in-built generator changes to produce a particular sequence of musical tones. The UMS series microcircuits easily fit into various electric devices including: alarm clocks, different musical toys for children, and, of course, doorbells. Let's take a look at a standard connection diagram of a UMS8-08 microcircuit. The microcircuit-synthesizer is the core of the device. The clock crystal resonator with a frequency of 32768 Hz. Any type of LED may be used, for instance, KD522. A bipolar transistor of reverse conductivity of the tested kt315 series or a similar one. A compact speaker with the voice coil resistance of at least 8 Ohms and the power ranging from 0.25 to 1 Watts. The schematic of the device is quite economical and operates in the range of 1.5 to 3 V. In the standby mode, the circuit consumes very little current. This is why it is possible to use no master switch. This is the most simple standard connection diagram of the microcircuit. There are a large variety of circuits with various additions and changes. For example, they may use a powerful input transistor increasing the volume by two times. An additional UNCh microcircuit for sound amplification also gives a significant result. Besides, some of these circuits operate at the minimum voltage of 3V. You can discover the capabilities of this microcircuit, if you assemble a simple musical device.