via multifunctional alarm and timer (555) circuit

(1) Introduction to circuit principle - Figure 3-13 shows a general multi-functional alarm and timing circuit. The timing range of this circuit is from 5min to 3h.
Timing components G, VD1 and VT1 form 555. Multiplier capacitance of the circuit. A DC voltage of 6~9V is regularly output from the CK1 socket, which can be used for
regular operation of radios, etc. Set Kl to the timing position and press AN. The ◎ pin of 555 outputs high level (6~9V). At the same time, VT2 is disconnected. When the timing time
is up, the ③ pin of 555 becomes low level, CK1 is output without voltage, VTZ is connected, the alarm sound of Fl and F2 and
the light alarm generated by F3 to F5 are generated. The AB terminal can be connected to various external sensors to form an additional sound and light alarm circuit. Embedded circuit
  (2) Component parameter selection. Components should be selected as shown in Figure 3+13. There are no special requirements.
  (3) The general multi-functional alarm and timer (555) circuit is shown in Figure 3-113.