Classical scheme of intercom system
Together with doorbells almost every building consisting of more than one floor there is built an intercom system. Currently the market offers advanced digital intercom systems in which electronic occupies a significant part. Each company offers its products and respectively provides diagrams and installation schemes.
Кey elements of which are built a classical intercom installation are carbon microphone (M) electro dynamic speaker (T) and power supply. This is one of the first circuits created and serves more to explain the principle of design of the intercom, but is fully operational.
Upon impact of sound pressure (speech) on the carbon microphone diaphragm (1) , it begins to vibrate In synchrony with these vibrations the clamping force of the carbonaceous grains (2) are changing , thereby changing the electrical resistance between the electrodes (3) and (4). When constant voltage U0 ( in the case 8V) is applied, the current through the microphone also is changing. If the microphone is incorporated into the primary coil of the transformer Tr , then in the ends of the secondary coil an AC voltage occurs , the shape of which corresponds to the sound pressure acting on the diaphragm of the carbon microphone.
Classic scheme of installation of door bell
Doorbells serve to signal the presence of a guest at the front door. In essence they are the most diverse – with mechanical bell melodic bells (e), wireless bells (e), etc. Here will be shown on a classical scheme such installation to which may be added and electron components. For example, to be replaced conventional electro-mechanical bells with electronic ones that have a variety of tunes.
Doorbells of an apartment consists of a bell placed in the entrance hall, two buttons – the front door of the apartment building (a boutonniere) and the front door of the apartment, connecting wires.
Power supply of doorbells for the entire building is performed by a general bell transformer. His classical performance is shown in Fig. 1. , the primary side is 220V/1A, the secondary side is with medium conclusion and accordingly 3V, 5V and 8V and power of 4VA. It is installed in the main switchboard at the entrance.
Wires are twisted pair of solid copper wire with insulation – PVU-A1-wire, insulation color blue and black. The temperature of the application it should not be less than -5 ° C. Section of the core is 0.5 – 0.75 mm ², the minimum bending radius is 10xD (for 0,5 mm ² D = 4,6 mm) the wires are as many as the number of apartments plus two. Both wires are common to all buttons respectively and all the bells. Installation of wires is hidden in the pipes through floors and junction boxes to buttons and bells for each apartment.
Doorphones and bells
1.Design of audio and video doorphones with capabilities to open outside door.
2.Desig of bell instalations