Features of installation of security radio channel systems.
There are a number of specific points in the installation of radio equipment, which are determined by the very principle of information exchange between all parts of the system.
For example, based on the passport data of the equipment, it is very difficult to give a 100% guarantee that the range of the radio transmitters is sufficient to fully cover the territory of a particular object. The technical documentation provides the range of radio signal transmission in direct visibility. It is clear that any object consists of walls, partitions, ceilings, doors, which make significant adjustments to the propagation of radio waves. Well-known phenomena in physics of absorption, transmission and reflection of electromagnetic waves come into play. Therefore, each object is unique in its own way. How can we determine whether a given system is suitable for installation at a specific object? Here, empirical observations come to our aid. Practice shows that in most cases, you can divide the passport range by 4-5 and get an idea of the range inside the building. If the value obtained in this way is 50-100% greater than the maximum distance between the receiver and the transmitter at the object, then most likely the installation will take place without serious problems. If the obtained value is approximately equal to or less than the maximum distance between these devices, then a radio signal repeater must be included in the equipment specification. It is also necessary to take into account that if the facility has several floors, then the actual range in the vertical plane may be less than in the horizontal plane. Below we will note a number of other provisions regarding the choice of location for installing the receiving unit and detectors.
Avoid nearby metal objects. All large metal objects are good screens for radio waves. This, firstly, prevents direct passage of signals, and, secondly, can lead to the interference effect — weakening of the direct signal by subtracting the reflected one. Make sure that the space around the receiver and detectors is free of large metal objects (metal doors and cabinets, etc.) by more than 50 centimeters.
Avoid nearby sources of radio interference. Make sure that the space around the receiver and detector is free of sources of electromagnetic radiation (computers, radio telephones, Wi-Fi routers, etc.). The recommended distance from these objects to the receiver and detector is more than 1 m.
Select the frequency range of the radio devices used. With the increasing use of wireless devices for various purposes, there is a significant contamination of the radio air with third-party signals, which have a negative impact on the reliability of radio channel security systems. This has a particularly strong effect on the operation of systems that use a frequency of 433 MHz to transmit data. Compliance with the rule of the previous paragraph, of course, helps to improve the reception of radio signals, but sufficiently powerful sources of radio interference can be located outside the protected premises. Therefore, the use of wireless equipment at a frequency of 868 MHz can significantly simplify the process of its installation at commercial and residential properties. The key advantages of using a frequency of 868 MHz over a frequency of 433 MHz are a significantly lower level of interference in the radio air and better penetrating ability of radio radiation inside protected objects. Therefore, if there is an alternative in choosing a frequency range within the range of one brand, it is preferable to use equipment with an operating frequency of 868 MHz. Additionally, we note that most systems have a radio diagnostic function for the presence of third-party signals on the operating frequency, and some even have the ability to select a frequency channel in the permitted frequency band.
Choose the correct location of the receiving device. It is recommended, if possible, to install the receiver or wireless control panel in the center of the protected area. In this case, the receiver will receive approximately the same signal from all transmitters.
Choose the correct orientation of the transmitters. In many systems, the antenna in the transmitters and receivers is oriented vertically. Accordingly, the horizontal location of the transmitter can lead to a decrease in range, which sometimes happens during installation. For example, a wired magnetic contact detector is usually mounted horizontally at the top of the door, so there is always a temptation to install a wireless detector in a similar way.
Don't forget about cable routing. When installing a radio channel system, you may need to route cables to power the following types of devices: radio signal repeaters, control keyboards, actuator control modules, sirens. The list of such devices may vary from manufacturer to manufacturer. For example, some manufacturers have fully autonomous sirens, while others have control keyboards that operate only on batteries.
Registration procedure for radio channel equipment
The basic procedure for installing radio equipment is registering all devices in the memory of the control device. In this regard, some similarity can be noted in the installation of a radio channel and wired addressable system. In both cases, the systems are addressable, i.e. only one detector is assigned to one zone. In general, the procedure for most systems is as follows. The control device is switched to the radio device registration mode, then a zone is selected for the detectors, then the transmitter of the detector is activated and the control device confirms the registration of the transmitter. Naturally, the step-by-step specific actions for different systems will differ. For example, in some systems, to enable the transmitter mode of the detector, you must first select the activation method: normal mode (by triggering the detector) or by tamper. Why might this be important? Imagine that all the detectors are already installed in their places. The receiver is in the mode of waiting for a signal from the detector to register it in the zone, and at this time a previously registered detector is accidentally triggered. As a result, the required detector will be outside the system, but the other detector will be registered in two zones at once, which can lead to unpleasant consequences. If you select the inclusion of signal transmission upon violation of the tamper contact, then the registration will always go as it should. Additionally, we note that the procedure for registering radio devices is recommended to be carried out before all devices are already installed in their places, for example, by simply placing them on the table.
The process of registering radio key fobs, remote control keyboards and sirens occurs according to a similar scheme. Only these devices are related to user numbers (not zones), remote controls or sirens.
In this article, we will omit programming the main properties of the system (security zone attributes, security sections, output operation, communication parameters with the central station), since in this regard there are no differences between wired and wireless systems.
Checking the communication channel between detectors and the control panel
Some systems use duplex communication — 2-way data exchange between the detector and the receiver. In such systems, the receiving device is in the mode of waiting for notifications with subsequent transmission of an acknowledgement signal. If the detector misses the acknowledgement signal, the detector transmitter increases the frequency of sending the radio signal. Some systems use an additional method to increase the probability of notification delivery — increasing the transmitter power in the detector and/or switching to another frequency channel in the permissible frequency band. In systems with one-way transmission, the acknowledgement signal from the receiver is absent by definition. To increase reliability, other methods are used in such systems. For example, instead of one message, a group of messages is sent. Moreover, each detector is characterized by a different time shift between messages, which can be randomly set at the manufacturer. If at some point in time the signals from two transmitters are completely synchronized, then at the following moments in time the signals from these transmitters will have a time shift. Thus, the receiver will register two messages without any loss.
In any case, regardless of the type of the system, one of the most important adjustment procedures is diagnostics of the level of incoming signals from the detectors. Specialists with experience in installing radio channel equipment know well that the reliability of the entire system directly depends on how competently the diagnostic procedure is carried out. In the diagnostic mode, you should achieve stable reception from each detector. If this rule is violated, then further operation may reveal cases of «loss» of radio devices. Almost all wireless systems provide the ability to indicate the level of the received signal. As a rule, manufacturers themselves indicate the required value of this parameter in the technical documentation. The fact is that the level of the received signal may change over time. For example, if for some device you received a reception level of 2 conventional units, and the instructions recommend 4-5, then when an extraneous radio signal appears, the receiver may miss the useful signal.
The diagnostic procedure for most systems is as follows. The control device is switched to diagnostic mode. Then the installer triggers the detectors one by one. When the control device receives a signal from a detector, it displays its level on the display (saving it in memory) and simultaneously emits intermittent sound signals (e.g. 1 signal – poor level, 2 signals – good, etc.). It is recommended to remove the detector from the place from which a low or satisfactory signal was received. In this case, it is necessary to try moving the detector to a new location and retesting. Even a small change in location can give a positive result. If the signal remains at a low level, then a repeater may be needed in the system. Therefore, it is recommended to carry out an initial express diagnostics even before all the detectors are installed in their places.
Features of installation of radio channel detectors
When installing passive infrared detectors, it is necessary to take into account the specifics of their operation. Unlike wired PIR detectors, wireless devices of this type operate in energy-saving mode. The essence of this mode is as follows. After the fact of detecting human movement, an internal timer is started in the detector, which is set to a certain time interval value (no more than 2-3 minutes). If during the timer countdown the detector again detects human movement, the timer is restarted from zero. In this case, there is no signal transmission to the receiver. This can continue many times if there are people in the room. Naturally, when the last person leaves the room, after the end of the timer countdown, the detector will go into the mode of readiness for radio signal transmission. Accordingly, the next activation of the detector will lead to sending an alarm message to the receiver. This mode was developed to increase the service life of the power source, since it is at the moment of radio signal emission that the greatest energy consumption occurs. Without the power saving mode, installing a wireless PIR detector in an office would drain the battery in a matter of weeks. After all, there are always people in the office during working hours.
The energy-saving mode only interferes with setting up the detector detection diagram. Therefore, a special testing mode is provided for setting up the detector. In this mode, the detector turns on the LED and transmits alarm notifications to the receiver every time it registers human movement in the detection zone (intersection of the detector detection sectors). Manufacturers use various methods to switch the detector to the testing mode. The first method is to change the position of the microswitch or install a jumper on special contacts. The second method is after power is supplied (the battery is installed). The third method is any violation of the tamper contact (opening the top cover of the detector housing). In the second and third cases, the detector automatically switches to normal mode after a short period of time (10-15 minutes).
The energy saving mechanism described above applies mainly to simplex radio channel systems. For duplex systems, the energy saving algorithm looks somewhat different. In such systems, the detector receives information from the receiver about the mode the system is in. If the system is disarmed, the detector simply ignores alarm events.
All other types of wireless detectors do not have such specific operating modes. Accordingly, their installation is similar to the installation of similar wired detectors. The only thing to pay attention to is the need to connect a power cable to natural gas detectors. In propane and methane leak detectors, the sensor is powered by a 220V network, and the transmitter is powered by a built-in power source.
In addition to the contacts for opening the case (tamper), which are available in all security detectors, some models of wireless detectors have sensors on the back of the detector case. Its main purpose is to control the fixation of the detector to the wall. That is, if the detector is torn off the surface, the transmission of a tamper alarm to the receiver is activated.
Maintenance of radio channel detectors (replacing batteries)
Many manufacturers use lithium batteries to power detectors, which have a longer service life compared to Alkaline batteries. The detector's passport usually specifies the average operating time of the detector under certain conditions. For example, for a magnetic contact detector, the number of transmitted signals (when opening the door) per day is specified. The average operating time of lithium batteries is 2-3 years, and the shelf life can be 5-7 years or more. Some manufacturers use a backup battery of lower capacity in addition to the main one. Although it should be noted that detectors send a signal about the battery discharge, as a rule, 2-3 weeks before the battery is completely discharged and the detector stops transmitting any messages to the receiver. Therefore, it does not matter how many batteries are in the detector, the main thing is that the receiving device will receive information in advance about the need to replace them. Naturally, this information can be read on the receiver display or, depending on the system configuration, sent as a special message to the service organization (via PSTN/GSM/GPRS/SMS/WAN channels). The battery replacement procedure itself is extremely simple — open the detector housing and change the battery.
Evaluation of time parameters for installing wireless systems
It is known that one of the main advantages of radio channel systems over their wired counterparts is significantly less installation time. To illustrate this, below is a table indicating the average time of the main procedures when installing a wireless system. As an example, we used installation data for three systems: Strelets (manufacturer Argus-Spectr), PowerMax Pro (manufacturer Visonic) and iConnect (manufacturer Electronics Line). The system includes: 20 detectors (PIK-10, fire smoke — 10), 4 radio key fobs, 1 control keyboard and 1 siren. The system is programmed from the control panel.
Note: these systems have their own step-by-step instructions for each procedure. As can be seen from the table, the total installation time for all systems is almost the same and ranges from 7 to 8 hours. The procedures that are performed in the same volume when installing wired systems are marked with an asterisk in the table. The share of these works takes up almost 80% of the total installation time. The time for registering a wireless detector and connecting a wired detector to a loop/power supply is approximately the same. Thus, the difference between the installation time of a wired and wireless system is determined mainly by different time intervals for laying the cable and diagnosing the radio communication. Moreover, laying the cable from the receiver to the detector can take tens of times more time than diagnosing the communication channel. Accordingly, the more detectors there are at the facility and the larger its size, the greater the time gain for wireless systems.