NE555 timing circuit using ±15V power supply

Introduction to the circuit principle In the circuit, in order to obtain bidirectional output
capability and operate under dual power supplies,
a floating differential operating voltage can be added to the power supply terminal of the NE555. The resistor Kun~Feng and the transistors
VT1 and VTZ form a voltage displacement network that can be used to generate the necessary
floating voltage. Capacitor C3 is used to suppress
the high-frequency vibration generated when the timer output jumps . ',
    (2) Component Parameter Selection Before component selection, as
shown in Figure 3, 11, there are no special requirements.
    (3) The NE555 fixed resistance circuit using ±15V power supply is as shown in the figure