This document discusses different types of doorbell systems. It describes traditional wired doorbells which use a transformer to power the bell. It also covers wireless doorbells which send a radio signal to activate a receiver unit inside. The document outlines doorbell options for deaf users, including vibration-based systems that provide tactile alerts and light-based systems that flash lights. Radio doorbells are also discussed as they trigger speakers throughout a home. Circuit diagrams are provided for sample wired and light-based alert doorbell designs.

2. A doorbell is a signaling device typically placed near an
entry door to a building.
 When a visitor presses a button the bell rings inside the
building, alerting the occupant to the presence of the visitor.
 Although the first doorbells were mechanical, activated by
pulling a cord.
But modern doorbells are electric — they are actuated by an
electric switch.
 A precursor to the electric doorbell, specifically a bell that
could be rung at a distance via an electric wire.
was invented by Joseph Henry around 1831.

4. In most wired systems, a button on the outside next to the door,
located around the height of the doorknob, activates a signaling device
(usually a chime, bell, or buzzer) inside the building.
There are two types of Door bells are there i.e
1.Wired Door-bell
2.Wireless Door Bell.
1.Wired Door-Bell:-

6. A doorbell transformer steps down the 120–240-volt AC electrical
power to a lower voltage, typically 10–20 volts.
The transformer's other terminal connects to one of three terminals on
the signaling device.
Another terminal is connected to a wire that travels to the other
terminal on the button.
Pressing the doorbell button, a single-pole, single-throw
(SPST) switch. momentarily closes the doorbell circuit. One terminal of
this button is wired to a terminal on a transformer.

7. The flat bars are tuned to two pleasing notes. When the doorbell button is
pressed, the first solenoid's plunger strikes one bar, and when the button
is released, a spring on the plunger pushes the plunger up, causing it to
strike the other bar, creating a two-tone sound ("ding-dong"). The
doorbell button contains a built-in radio transmitter powered by a battery.
When the button is pushed, the transmitter sends a radio signal to the
receiver unit, which plugs into a wall outlet inside the building. When the
radio signal is detected by the receiver, it activates a sound chip, which
plays the sound of gongs through a loudspeaker, either a two-note "ding-
dong" sound, or a longer chime sequence such as Westminster Quarters .
wireless Door-Bell:-
To avoid the possibility of nearby wireless doorbells on the same
radio frequency interfering with each other, the units can usually be set
by the owner to different radio channels.

9. If a second doorbell is used, it is wired to the other solenoid, which
strikes only one of the bars, to create a different sound.
In recent decades, wireless doorbell systems have become popular,
which don't require wiring in the walls.
The simple task of answering a doorbell becomes a challenge
when a person is deaf or hard of hearing. A doorbell for a deaf
person needs to use something other than sound to alert the
person of a visitor.
There are a number of options available to help accommodate
the need to make a doorbell for a deaf person.

10. Basically for deaf we can use two types of Door-bells these are
1.Vibration Based Door-bell.
2.Light Based Door-Bells.
3.Radio Door-Bell.
1.Vibration Based Door Bell:-
The Person who are hearing Impaired they can’t hear the voice of the
Door bell but they can feel the vibration.
So in order to make them feel and get them know that someone is in the
Door we use the Vibration based door bells.

11. Which gives a little shake to the person when the switch is pressed
and
Get the deaf person some sense that someone is there in the Door.
The vibration sensor is usually adjustable on a door knock alert
system, so the level of vibration that triggers the alert is determined by
the person using it.

12. Light doorbells, or visual alerting devices, use light to alert a person
that someone is at the door.
These doorbells range from a single light connected to the doorbell to a
more elaborate system that flashes all the lights in the house.
These doorbells are either activated by a doorbell button or a door
knock alert system.
With a door knock alert system, when someone knocks on the door a
vibration sensor unit detects the vibration caused by the knocking and
thus signals a bright light to flash.

15. This circuit provides a delayed visual indication when a door bell
switch is pressed. In addition, a DPDT switch
can be moved from within the house which will light a lamp in the
door bell switch. The lamp can illuminate the words "Please Wait" for
anyone with walking difficulties.
DIODE 1N4001
BULB 2 NOS.(12V,60mA)
PUSH BUTTON.

16. DPDT SWITCH.
RESISTOR (22R,10W)
RESITOR(100K)
RESISTOR(47R)
CAPACITOT(47u)
TRANSISTOR(ZTX550)
FUSE(500mA)
BATTERY(12V)

17. The circuit uses standard 2 wire doorbell cable or loudspeaker wire.
 In parallel with the doorbell switch, S1, is a 1N4001 diode and a 12
volt 60mA bulb.
The bulb is optional, it may be useful for anyone who is slow to
answer the door, all you need to do is flick a switch inside the house, and
the bulb will illuminate a label saying Please Wait inside the doorbell
switch or close to it.
The double pole double throw switch sends the doorbell supply to the
lamp, the 22 ohm resistor is there to reduce current flow, should the
doorbell switch, S1 be pressed while the lamp is on..

18. The resistor needs to be rated 10 watts, the 0.5 Amp fuse protects
against short circuits.
When S2 is in the up position (shown as brown contacts), this will
illuminate the remote doorbell lamp.
When down, (blue contacts) this is the normal position and will
illuminate the lamp inside the house.
 Switch S1 will then charge the 47u capacitor and operate the transistor
which lights the lamp. As a door bell switch is only pressed momentarily,
then the charge on the capacitor decays slowly, resulting in the lamp
being left on for several seconds.

19. If a longer period is needed then the capacitor may be increased in
value.
This is all about the working circuit diagram.
It is for someone who is not entirely deaf but can't hear a regular
doorbell, a radio doorbell might be the answer.
Radio doorbells send out signals that trigger speakers throughout the
house or apartment.
These speakers then make a loud noise to alert the person that someone
is at the door.

21. Like Light doorbells and door knock alert systems doorbells, radio
doorbells are generally wireless devices. They are also probably the
most affordable option of deaf-oriented doorbell.
It is all about the radio door-bell.
Here we got all the types of door-bell systems their working and benefits
as well as we got different types of door-bells systems for deaf these are
Vibration Based Door-bell , Light Based Door-bell and Radio Door-bell
and their workings.
It has a future aspects and it can be developed further by using
integrated circuits and micro controllers and some intelligent sensor.