We found this circuit in an 80s Intersil documentation. Modern equivalent operating systems can be used. The potentiometer adjusts the detection level.
This 3-step level indicator uses only passive components. LEDs are common and trimpots can be 4k7...
The 4046 consists in a PLL with na internal oscillator controlled by voltage (VCO). Figure bellow...
This regulated power supply can provide currents up to 1 A to a load. The transformer may actually have...