Need the complete document on "switch less calling bell"

circuit diagram of calling bell
Here we have "ring duration (how long it should be a button press on the ring) 555 timer ICS to control, are using one, and other sound produced by the Bell is to control the frequency of oscillation. The first IC IC anvasthit ekasthitik mode will work and will work in the other.
"Ring duration" to control, we Reset PIN 555 timer IC (4) other 555 timer IC production first pin (3) is connected. As long as the first IC output pin 555 timer IC wag more, second. 555 timer IC PIN Reset PIN, the fourth of IC is the same thing, this PIN is connected to the ground pin, if this high positive voltage is connected to work and changing the IC/ The capacitor will not discharge.
Above figure shows the circuit diagram for doorbell. Here we can see that First 555 timer IC is configured in Monostable mode, means it will go high and low only once if triggered with Trigger pin 2. Variable resistor RV1 is used to control the ring duration, means how long will be the output pin 3 will be high. 555 timer IC principal says that “Output PIN 3 will be HIGH as long as the capacitor (C1) will charge to 2/3 Vcc (battery voltage) and as soon as capacitor charges to 2/3 Vcc, Output pin 3 becomes LOW until the capacitor discharges to 1/3 Vcc”. This charging and discharging will happen once in Monostable mode. And it happens continuously in Astable mode. We can calculate the Ring duration (t) as follows:
t = 1.1*RV1*C1 seconds
We have also connected a LED at output of first IC, which will glow till doorbell ring.
Second 555 Time IC is configured in Astable mode which will oscillate till t seconds. Here we can also control the frequency by adjusting the value of R2 and/or capacitor C2.
Frequency =1/T= 1.44/((R1+R2*2)*C2)
TL (low time)= 0.693*R2*C2
TH (High Time )= 0.693*(R1+R2)*C2
D= Duty Cycle= (R1+R2)/(R1+2*R2) %
We have used 100k R2, but a variable resistor (100k or 1M) can also be used to instantaneous change the TL and TH.
Basically the main difference between Monostable and Astable 555 timer circuit configuration is that, in monostable, trigger pin 2 is trigger manually by a switch while in Astable trigger pin is automatically triggered when capacitor discharges to 1/3 Vcc. Also in Monostable mode, there is no resistor between PIN 6 and 7, while in Astable mode Resistor between 6 and 7 play a key role.
Pin 5 of the 555 Timer IC, should be connected to ground via .01uf capacitor when not used. Pin 5 is the control pin which is at the 2/3 Vcc. Pin 5 is the inverting end of comparator inside 555 Timer IC, which is used to compare the voltage with Threshold pin 6 (inverting end of comparator).