Comparison Alligator A-3S vs Sheriff APS-2600

The number of independent security zones provided in the alarm system.

Each independent zone has its own set of sensors — for example, one zone can cover the doors, the second — the boot, the third — the hood, etc. This, in particular, makes it possible to determine in which place an attempt was made to penetrate, a blow occurred, etc., and to give an appropriate signal — up to showing a specific place of operation on the display of the key fob with two-way communication (see "Type of communication"). In addition, separate activation / deactivation or a time difference can be provided for individual security zones. For example, upon auto-arming (see "Security and Protection"), the alarm for the doors can be activated immediately, and for the boot — for some time later, which will make it possible to calmly pick up things from there.

The simplest modern car alarms have 1 – 2 security zones, in advanced models this number can exceed a dozen (which, in particular, allows you to provide your own security zone for each individual door).

— Quiet security mode. This mode assumes the complete absence of sound signals in the event of an alarm. In models with one-way communication (see "Type of communication"), the warning is usually carried out by light signals (flashing headlights), with two-way notification sent to the key fob or other device. Anyway, the silent mode can be very useful when extra noise is undesirable — for example, at night, when a siren could disturb people around.

— Silent setting / disarming. The ability to silently turn on and off the security mode, when the alarm reports a change in the operating mode only by light signals or notifications on the key fob (or other control device). This function will be very useful if you need to keep quiet (for example, at late hours of the day or early in the morning), or if you do not want to give others (including possible intruders) unnecessary signals about the state of the machine.

— Automatic arming. Possibility of automatic arming of the alarm system. Usually, this happens after the ignition is turned off and all doors are closed. The meaning of this function consists of two main points. Firstly, it reduces the likelihood of forgetting to turn on the armed mode and leaving the car unprotected. Secondly, automatic arming eliminates the need to once again give signals from the key fob and makes it difficult for intruders trying to...read the signal using a scanner.

— Arming delay. The ability to delay the automatic arming of the car (see above) for some time — usually within a few minutes. This feature will be especially useful if, after getting out of the car, it often becomes necessary to return to it — for example, to pick up some things.

— Security with the engine running. The ability to arm the alarm when the car engine is running. This feature can be very useful if you need to go away, leaving the car unattended, and it is undesirable to turn off the engine — for example, if it is turned on to warm up before an urgent trip.

— Security of the perimeter. Perimeter protection provides protection against illegal entry into the car: an alarm system with this function is able to respond to door openings, and in the case of using additional limit switches (see “Supplied Contents”), also to opening the hood and/or boot. In this case, the signal can be triggered not only when opening directly, but also when trying to open.

— Blocking a stolen car (Anti-Hi-Jack). The ability to block the engine or control in case of theft or forceful seizure of the car. The specific implementation of this function may be different. For example, some alarm models provide protection against robbery: if the driver's door is opened with the ignition on, the timer starts, and if after a while the driver does not turn off the Anti-Hi-Jack (by pressing a hidden button, entering a code, or in another way that is not available intruder), the system blocks the car. In other models, the activation of this function can be carried out remotely — for example, by a signal from a mobile phone. Also, blocking can be accompanied by other actions of the system — for example, turning on a siren or locking doors to detain an intruder.

— Disarming in two stages (AV). When using this function, to completely disarm the car, you need to send a command from the control device twice: the first command unlocks only the driver's door, and the rest open only when the button is pressed a second time. In this way, protection is provided against thieves — “purse holders” and other intruders who can enter the car through doors that are not controlled by the driver.

The maximum distance at which the ability to control the alarm from the standard key fob remains. In other words, this is the greatest distance from which the driver can give the system a control signal. This parameter should be distinguished from the reception range (see below): due to their small size, transmitters in key fobs are made relatively low-power, and the control range from the key fob inevitably turns out to be less than the signal reception range on the key fob (if the latter is provided at all in this model).

When choosing by this parameter, note that the control range is indicated for perfect conditions — that is, line of sight with a minimum of interference. The actual “range” of the key fob will inevitably be less, especially in the face of an abundance of obstacles. At the same time, modern car alarms most often have quite impressive range indicators. Thus, a distance of less than 500 m is considered rather small in this sense; 500 – 750 m is the average value, 750 – 1000 m is above average, and in some models a range of more than 1 km is claimed.

Availability of alarm protection from scanning ; if the characteristics specify the type of such protection, it is also given in this clause.

Scanning is used by attackers to intercept the control signal from the key fob; by forging such a signal, the hijacker can safely open the car. Accordingly, this protection is aimed at preventing such hacks. And its main types nowadays are dynamic code and dialog code, here are the features of each of these methods:

— Dynamic code. The general principle of dynamic coding is that each time you press the button to turn on or turn off the alarm, the key fob gives a new, unique signal. Most often, the Keelog algorithm is used for this; it assumes that the signal from the key fob contains data on the serial number of the device, the number of clicks and the secret code that the central unit also “knows” (this code is written at the factory and is unique for each alarm). Based on the serial number, the system performs general identification of the key fob, the click counter confirms that the signal has not been sent before, and the secret code acts as an encryption key. Thus, even if an attacker intercepts and copies the signal from the key fob, this signal will be outdated and, accordingly, useless; and it is impossible to decipher this signal and reproduce the desired version without a secret code.
The main advanta...ge of systems with dynamic coding is simplicity and, accordingly, low cost. However, this method in itself is less perfect than the dialog code, it provides a lower degree of protection against interception and hacking — with the help of the so-called dynamic code grabber with a jammer, an attacker can still intercept the control code under certain conditions and open the machine. However this procedure is quite complicated and does not give a guarantee; so in general, dynamic code is a good option for inexpensive cars that are not particularly attractive to professional crackers. But for maximum protection, it is still better to use dialogue systems.

— Dialogue code. Protection operating on the principle of “friend or foe” recognition: before giving a control signal, the key fob and the central unit exchange service data, identifying each other and making sure that the signal comes from the rightful owner. This is done in the following way. When you press a button on the key fob, it sends a connection request with data about its serial number. The central unit checks the serial number and, if the result of the check is positive, sends a randomly generated number to the key fob. The keyfob processes this number according to a certain algorithm and sends the result (together with a request for action) to the central unit, which performs calculations according to the same algorithm; if the results agree, the defense gives the go-ahead to execute the command. The algorithm used for calculations is unique in each individual signaling, and so-called hash algorithms are used to encrypt the transmitted data. Due to this, the dialogue code is almost impossible to crack: for this, the attacker must intercept 3 data packets (request, riddle, guess) and decrypt 2 of them, while without knowing the key (embedded in the alarm itself and inaccessible without physical access to the device), such a decryption nowadays is inaccessible even to the most powerful computers.
Dialogue systems are naturally somewhat more expensive than dynamic ones, but this is more than offset by a high degree of security.

The delivery set includes, in addition to the main alarm unit, it can also include additional elements, including a CAN bus, a LIN bus, a blocking unit, an immobilizer, a limit switch, a volume sensor, an interior temperature sensor, an inclination sensor, a movement sensor, a boot opening relay, siren. More details about them:

— CAN bus. The ability to connect the alarm to the car's electronic CAN bus. Many modern car models are equipped with such a tyre (and their number is constantly increasing); it allows you to receive information from the car's own built-in sensors about the status of its various parts, from the opening of the doors and boot to the position of the gear knob and the readings of the speedometer and tachometer. To date, connecting a car alarm to the CAN bus is the most convenient option, because. does not require intervention in the standard wiring of the car and greatly simplifies the process. Note that the module itself can be either built-in (in such cases, the CAN connection is standard) or external. In the absence of a CAN module in the kit, usually, it can be purchased separately, but...this is more difficult and troublesome than immediately acquiring a CAN-compatible signaling.

— LIN bus. The alarm can be connected to the vehicle's LIN bus. Integration with the LIN machine interface allows the security system to control and interact with some of the car's original functional systems. This can be an engine preheating system, a climate control system, etc. The LIN (Local Interconnect Network) interface combines the peripheral and secondary functional systems of the car, but it is impossible to control the operation of the engine or transmission through it. The main systems of the car are controlled via the CAN (Controller Area Network) interface.

— Lock block. Availability of the block of blocking of the engine in a complete set of delivery of the alarm system. Such a module, when triggered, blocks the engine or another element of the car (for example, the starter), preventing the attacker from leaving the car. Activation can occur by triggering an alarm or by pressing the "Anti-Hi-Jack" button (see "Security and Protection"). There are two main types of blocking block — with normally closed contacts (NC) and normally open (NO). In the first case, the blocking relay is de-energized in the normal state, and when the alarm is triggered, it becomes energized and opens the circuit. This option is convenient in that if the alarm fails, the machine will not be blocked, but the reliability of the NC from the point of view of safety is somewhat lower than that of HP. In turn, the blocker with normally open contacts is switched on if the voltage on the control relay is lost. Disabling such a system is somewhat more difficult (especially if the control is carried out via the CAN bus), however, in the event of a failure in the auto or alarm electronics, the car remains stationary. Some alarms provide universal blocking blocks that allow the owner to choose the format of operation — NO or NC — at his discretion.

— Immobilizer. Immobilizers are electronic devices designed to prevent the movement of a car in the event of illegal entry into it. Immobilizers can have different designs and areas of influence: for example, some open the starter or ignition circuit, others turn off the fuel injection controller, others send a control signal via the CAN bus (see CAN module), putting the entire system into an “inoperative” state. The immobilizer can be disabled by the driver using a key, tag, secret button, code, etc. Such devices, in fact, insure the main alarm in case of its failure or hacking: even if an attacker manages to get into the car, he will not be able to steal the vehicle. This is the difference between immobilizers and the blocking systems described above — they can work even when the alarm is "silent". Note that immobilizers are distinguished by a high degree of secrecy. So, a well-installed module is carefully hidden from prying eyes, its operation is often disguised as a malfunction (for example, a dead battery is simulated), and some models do not work immediately, but some time after the start of movement. The latter increases the likelihood that the attacker will be in a stalled car in the open and hide without trying to complete the theft. Immobilizers are installed in many cars as standard equipment, directly at the factory, however, the degree of safety of such equipment is low, and many motorists prefer to supplement it with non-standard devices. Of course, in the absence of an immobilizer, you can buy it separately, but this is more troublesome than buying a ready-made kit.

— Antenna module. The presence in the delivery set of the signaling of a separate block containing an active antenna. Such a unit greatly enhances the range of the transmitter, allowing you to receive notifications from two-way alarms (see "Type of communication") at a distance of 1 km or even more. Also, a driver call button or sensor is often installed on the antenna module (see "Functions").

— Limit switch. The presence of a limit switch (one or more) in the car alarm delivery set. The most popular application of limit switches is as sensors that monitor the opening of doors, boot, hood, gas tank cap, etc.: in the closed position, the door or lid presses the switch, and when opened, it releases it, to which the alarm reacts. Note that many modern cars are equipped with their own limit switches — for example, in the doors; they are normally responsible for turning on the lighting in the cabin, but alarms can also be connected to such switches. At the same time, firstly, attackers usually know the location of standard "limit switches" and can block them without any problems, and secondly, there are car models without such switches. Having separate limit switches, you can install them at your discretion, including in non-standard and most unexpected places for the hijacker.

— Volume sensor. The presence of a volume sensor in the delivery set of car alarms. Such a sensor works on the principle of a sonar: it periodically emits an ultrasonic signal and analyzes its reflection, thus “observing” objects in the cabin, and when the situation changes, it gives an alarm. In this way, protection is provided against "silent" penetration into the car — for example, with cutting glass, to which shock sensors and limit switches do not respond: the volume sensor will detect an intruder not noticed by other systems. There are also external sensors that monitor the situation around the car; when triggered, they do not turn on the main alarm, but give a relatively quiet signal, designed mainly to warn a person who has approached close that the car is on an alarm. The ability to connect such sensors is available in many modern car alarms, however, sensors are rarely included in the delivery set. So if you want to immediately get a system with such a function, without buying additional equipment, you should choose among the models that are initially supplied with volume sensors.

— Temperature sensor in the cabin. The presence of a sensor that monitors the temperature in the cabin, in the alarm package. This feature provides additional information to the driver, allowing him to assess the conditions in the cabin directly from the alarm key fob, without opening the car or approaching it, and take action if necessary — for example, leave the house a few minutes earlier to warm up the interior for a comfortable ride. In addition, the temperature sensor can also serve as an intrusion warning: for example, in cold weather, opening doors or windows leads to a sharp decrease in the temperature in the cabin, which can be noticed even if the intruders were able to open the car without triggering an alarm.

— Tilt sensor. As the name implies, the tilt sensor detects changes in the slope of the car body. Thus, for example, the system "takes care" that the wheels are not removed from the car. After all, to do this, you need to slightly raise the body. If a car thief decides to do this, then the tilt sensor will instantly detect manipulations with the body and immediately raise the alarm. The tilt sensor is one of the main sensors in many security systems for cars and motorcycles. Such a sensor can be found both in low-cost car alarms and premium security systems.

— The displacement sensor captures any mobility of the car: the car drives on its own, it is moved by a loader or in tow, it shifts from impact or rolls back due to a weak hand brake, etc. Having fixed the fact of the car’s mobility, the sensor activates the alarm. Often used in conjunction with a tilt sensor.

— Boot opening relay. The presence of a boot opening relay in the car alarm delivery set. If the car has an electric boot drive, you can connect it to this relay and control the opening / closing of the boot through the alarm key fob — this is much more convenient than pressing the button in the cabin every time.

— Relay with block. The presence of a relay with a block in the car alarm delivery set. This relay is used to connect additional external equipment to the alarm system — for example, a limit switch under the gas tank cap; the block also serves to attach the relay to the body of the car.

— Siren. The presence of a siren in the car alarm delivery set. The siren in this case is a sound warning unit that provides for the supply of characteristic sound signals. Note that such a unit is not always included in the delivery set, and if it is not available, you either have to buy the siren separately or connect the alarm to the horn. So if you want to immediately buy an alarm with your own sound signal, you should clarify the configuration of the selected model.

The number of additional channels provided for in the design of the car alarm. Each individual signaling channel is used to connect and control certain equipment. The main channels of the system are considered to be those that initially have a certain “specialization”: for example, one channel controls the siren, the second controls the headlights, the third controls the engine start, the fourth controls the boot opening, etc. However, in addition to them, additional channels can be provided that do not have specialization and are used for very diverse purposes, at the choice of the owner — for example, to control the heating of the passenger compartment or the rear window. The number of such channels in modern car alarms can reach eight; you should pay attention to this parameter if you want to connect equipment to the system that is not provided for by specialized channels.