The melody changes automatically, it sounds completely, pressing the call button does not turn on the next tune, if the previous is not finished.VD1-VD4 with any iobr more than 400,VD5-VD8 with I PR 0.1 A and above, ZQ1-hour quartz, BA1 0.4 W 8th. DA1 UMS (u pit 1.35 V-2.0 V). PR1-improvised in the form of a segment of wire with a diameter of 0.05-0.08 mm and a length of about 1cm. Voltage less than 6.3 V (operating voltage C4) on the output of the diode bridge depends on R2.
To increase the ringer volume, you can increase the voltage feeding the amplifier on VT1, using larger capacity C1 and C4 to the appropriate voltage. C6 is chosen of sufficient magnitude to switch to another tune after the break in the previous. From C5 depends on the charge rate is C6 and the time after which a change of tune (usually manages to sound 1-2 notes of the previous song), C5 also impact on the required capacity of C6, C5, C6 should be the minimum capacity.
You should observe safety precautions when mounting the device, i.e. it has a transformerless power supply.
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