CELL GUARD

CELL GUARDToday, phone operators, representing a population of mobile communication services, even in remote regions have made their rates available to most consumers. Constantly updated market of mobile telephones (AIT) allowed to acquire outdated but workable model for a symbolic price. Given this, anyone who is familiar with the basics of electrical engineering are given the opportunity to make the mobile phone almost free, automatic Secretary, who will notify the owner about the state of its protected values; whether it be apartment, a country house, safe, car or access to a personal computer. Now cellular telephone connected by the following method with a sensor that will automatically inform the owner about the condition of the protected property, wherever that may be. This is my article.

 
Wireless sirens were popular before, but then they used the radio mostly on civilian (27 MHz) range.
 
The proposed device is much easier alert via radio.
 
Every mobile phone function emergency call button – she will be in demand.
 
All additional work regarding the cell phone boils down to 4 steps:
 
1. To enter the phone menu and to store a fast call cell phone number or landline number, where it will be necessary to report the change state of the controlled object.
 
2. Carefully open the panel case cell phone (in flat keys) and a miniature soldering iron of 25 W (the voltage 6… 12 V) solder the two thin mounting wire type MGTF-0.3 to key contacts, for example button “1”. Button can be used and other, as well as a few buttons to alert different users in different situations.
 
3. The conductors must have a length of not more than 1 m and at the other end to connect with miniature connector, such as RSH-2N. Even better, if the leads are placed on the screen, which is connected to ground (minus power supply).
 
4. To build a simple device adapter (Fig. 1) that receives a signal from the sensors installed on the protected object and connect it according to wiring diagram
 
These steps are able to do today every student.
 
The device is assembled on the chip К561КТ3. In point of Ewha woman applied a control voltage from any of the sensors, such as reed switch, installed on the front door is opened. How to connect reed switch to power illustrates the switch S1, shown for example as a dotted line. The sensors can be different, including the issuing of a pack of pulses.
 
The input signal passes through limiting resistor R1 and is supplied to the oxide capacitor C1 (not passing the DC component of the voltage). Thus, even with prolonged exposure (for example, with the closure of S1), the control input IC-switch will do only a single pulse. Diode VD1 protects the control input of the channel from the surge voltage, and the resistor R2 shunts the input (pin 13), to treat possible electrical interference causing false actuations of the switch at the input of each channel are field-effect transistors, providing the high sensitivity chip.
 
Fixed resistors type MLT-0,25, MF-25 and similar. Oxide capacitor C1 type C50-29 or similar. The Zener can be replaced КС156А, BZX55 other suitable.
 
The power source for this device is stable with step-down transformer.
 
Electric diagram of the device adapter and its connection to MTA
 
Electric diagram of the device adapter and connect it to the MTA
 
After connecting to the cell phone role of the button performs electronic key visual silently and inconspicuously. It remains only to periodically monitor battery cell phone.
 
Help for those who want to use several sensors with notification to multiple numbers from a mobile phone: Fig. 2 shows a diagram of the connections and the Pinout of the chip switches К561КТЗ, К564КТЗ, К1561КТЗ, К176КТ1 (they are all interchangeable, but the power supply voltage К176КТ1 -9).
 
Chip К561КТЗ and analogues represent the four switches with the same diagram and Pinout. Equivalent circuit of a switch (electronic switch) – a single pole. This means that it only works for a short electronic contact output (for example, pin 1 and
 
2, 3 and 4, and so on) at the control signal input.
 
Control signal (pulse) DC voltage 2 -10 V (for chips К176 series – up to 9 In). Thus, for the circuit outputs an active level on input must be high logic level, applied to CMOS chips. The channel resistance in the open state – 80 Ohm (500 Ohms for К176КТ1). From this parameter, by Ohm’s law, knowing the applied voltage, you can calculate the switching current. Channels are independent, each can switch between the digital voltage levels to the IP, or analog levels (another nice feature of this chip type) peak-to-PI/2.
 
When a load of 10 ohms at a frequency of 10 kHz the ratio of the signals at the output of the channel in the closed and open States of no worse than 65 dB. The degree of isolation circuit from a channel corresponds to a resistance of 1012 Ohms. Signal with a frequency of 900 kHz to 1 kω loads from the channel into the canal is estimated at – 50 dB. The delay time of signal propagation in the channel is from 10 to 25 NS.
 
Switches of this type are universal. Therefore they are very popular in the following nodes: switches-multiplexers, keys, sampling the signal, the interrupters-modulators for operational amplifiers, switching keys, modulators-demodulators. You can make switches for non-standard ADCS and DACS, as well as components digital control of frequency, phase, gain signal. It is convenient to do “tie” and mix some signals into others.
 
It is for its intended purpose chip К561КТ3 is used for switching keyboard cell phone, the construction of which from each other is virtually identical.
 
What you need to know about the features of mobile communication for everyone…
 
SECURITY
 
As a rule, the MTA can run on a distance of 1500 m from the base station.
 
Each mobile unit is assigned to the electronic serial number (ESN), which is encoded in the microchip during manufacture. Activating a SIM card (Subscriber Identity Module) is a microchip that “stitched” the subscriber number of the mobile telephone apparatus receives a mobile identification number (MIN).
 
The area covered by the GSM network is divided into separate, adjacent to each other cells (“honeycombs”) – hence the name “cellular communication”, the center of which are the receiving-transmitting base station. Usually, this station has six transmitters, which are located with a beamwidth of 120° and provide uniform coverage of the square. One secondary modern station can simultaneously serve up to 1,000 channels. The area of the “cell” in the city is -1 about 0.5 km2, outside the city, depending on geographical location, it can reach 20 and 50 km2. Telephone exchange in each “cell” is controlled by the base station, which receives and transmits signals in a large frequency bandwidth (dedicated channel for each cellular telephone minimum).
 
A base station connected to wired telephone network and is equipped with equipment conversion high frequency cell phone signal in the low-frequency signal of a wired telephone, and Vice versa, which ensures the pairing of these two systems. Technically modern equipment base station covers an area of 1 m2 -3 and is within the one small room where her work is carried out in automatic mode. For the stable operation of such a station need only a wired connection with a telephone node (ATS) and the mains supply of 220 V. In towns and cities with a large cluster of transmitters of base stations are on the roofs of houses. In the suburbs and open countryside used the tower in several sections (they are often seen along the highway).
 
General diagram
 
The General scheme and “Pinout” of some circuits switches series К561, K564, К176
 
The coverage area of neighboring stations in contact. When moving a telephone between the coverage areas of adjacent stations it is registered. Periodically, with an interval of 10…60 min (depending on operator), the base station emits a signal service. By adopting it, the mobile phone automatically adds it your MIN – ESN-number and transmits that code combination to the base station. So carried out the identification of a particular MTA, the account number of the owner and the binding machine to a zone in which it is at the moment. This point is very important – at this stage it is possible to control the movement of the object, and who benefits from it – is another question -all…
 
When a user connects with someone on your phone, the base station allocates one of available frequencies of the zone in which it is located, gives his call on purpose and makes the appropriate changes to his account (makes a withdrawal).
 
If the user during a call, moves from one communication zone to another, the base station leave the area (cell) automatically translates the communication signal on a clear frequency adjacent areas (cells).
 
The most vulnerable from the point of view of possibility of interception of negotiations (listening) is an analog mobile cell phones. In our region (St. Petersburg) this standard NMT450 changed in 2005 (but it still exists in Belarus). Confident communication when the distance from the base station in such systems directly depends on the radiation power of the transmitting cell phone.
 
The arrival of almost every family comfortable cellular communication is an essential reality of time. But it imposes on the user and certain nuances. Work cell phone allows you to identify how the user’s current location and movements in the past in two ways.
 
One of them is the method of purposeful direction-finding of the cellular phone, determining the direction to the transmitter operates from three… six points and giving the notch location of the transmission source. The peculiarity of this method is that it can be used at anyone’s disposal.
 
The second method is through a cellular operator, which automatically and continuously detects a location of a specific subscriber in the moment, even in the case when he doesn’t talk. This registration happens automatically identifying service signals transferred enabled cellular phone to the base station (this was discussed above). The accuracy of determining the location of the subscriber depends on a number of factors: the topography, the presence of interference and signal reflections from buildings, position of base stations and their load (the number of active mobile phone operator in the cell), the size of the cell. Hence, the accuracy of determining the location of subscribers of cellular communication in the city is significantly higher than in open areas and can achieve a spot with a diameter of several hundred meters. Analysis of data on the communication history of the user from different base stations (with what and at what station were submitted to the call, the call time and the like) allows to reconstruct all the movements of the subscriber in the past. Data is automatically captured from the network operator (for billing and not only…), since these charges based on duration of use of the communication system. These data can be stored for several years, and this time is not yet regulated by the Federal law, but only departmental regulations.
 
More difficult to intercept the conversation if it is conducted from a moving vehicle as the distance between the cell phone user and DF equipment (if we are talking about an analog connection) is constantly changing and if these objects are removed from each other, especially in rough terrain, and among the houses – the signal weakens. With fast movements the signal is translated from one base station to another with simultaneous change of the operating frequency is difficult to intercept the entire conversation as a whole (if it is not conducted purposefully with the participation of operator), as for finding new frequencies will take time.
 
The implications of this can be done independently. For a leave only a recommendation to turn off your cell phone if you don’t want your whereabouts became known.
 
IT IS PARTICULARLY IMPORTANT
 
Modern MTA is able, moreover, to record “non-phone conversations” its direct owner. What does it mean?
 
Modern MTA’s can be included in voice mode for a given program, or automatically, without the authorization of its owner. Not the fact that every MTA writes the speech and the voice of the owner, and then sends the information, but such a possibility in the modern MTA technically provided. This factor should be considered in the operation of its “mobile phone”.
 
How is the transfer of information in the ether? Information (package of digital signals-pulses, which are called time slots) takes the nearest MTA station-Sota operator. The duration of a service session of MTA with the base station can last from fractions of second to several seconds.
 
These sessions official communication constantly when cell phone is switched on. Initially this happens the IMEI of your MTA. This number (issue described above) it is better to find out directly (buying or operation of MTA) and to write down somewhere away from prying eyes.
 
PRACTICAL INNOVATIVE SOLUTIONS
 
Connecting through wires of small cross section (for example, using flexible circuit insulated wire MGTF with a diameter of 0.6 – 1 mm) to the conclusions of the contact pairs on the keyboard, MTA, you can duplicate the clicking of a button, using the normally open conventional (low current) of the solenoid. This can be done in various professional and Amateur design, including those described in the beginning of the article.
 
An important advantage of the mobile telephone control – by the contacts of low-current electromagnetic relays is the lack of galvanic connection of the control device and keyboard of the phone.
 
The last caller (from the redial list), you can call using only one button (except power button MTA or buttons to unlock the keypad when this mode is enabled). In most MTA’s communication with the subscriber number was dialed last can be done by pressing only one button, not two (as described in some articles) – just clearly explored and menu for your “mobile phone” and use the “manual” programming (as described in the user manual).
 
In the opened housing of the mobile phone to the pads of the button “call” wires MGTF fluster two conductors with a length of not more than 50 cm For these purposes, use a low power soldering iron with a power of 25 W and a voltage not exceeding 24 V.
 
Terminal device, which closes the contacts can be anything from alarm to alarm egg. The important thing is that in case of violation of loop protection or alarm will close the contacts of the control relay, which means that the MTA will send the call to the preprogrammed number to notify about the state changes of the controlled parameter.
 
Received the call, can only look at the number of the caller (in most cases it is defined normally). If the phone number involved in the security system – then the burglar alarm went off.
 
A. KASHKAROV, St. Petersburg

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