Comparison Amazfit T-Rex 2 vs Amazfit GTR 3 Pro

Types of notifications, as well as basic voice communication features supported by the gadget.

— Call notifications. Notifications about calls coming to the smartphone connected to the gadget, and for watch-phones — about calls to the watch itself. In classic smartwatches and fitness trackers (see "Type"), the specific functionality of such notifications can be different — from the usual sound or vibration signal to the ability to see the caller's number on the screen and accept/reject the call. But anyway, such notifications are often more noticeable to the user than the own signal of a smartphone deep in a pocket or bag.

— SMS notifications. Notifications about SMS messages received either on a smartphone connected to the gadget, or on the gadget itself, if it is capable of receiving messages (all watch phones and many children's beacons have this capability, see "Type"). The specific features of notifications can be different — from the icon "you have received a message" to the ability to read SMS and reply to it. Anyway, this feature often provides additional convenience — at least it reduces the likelihood of missing an important notification, and often also eliminates the need to once again take the phone out of your pocket / bag.

— Voice control. The ability to control the device through voice commands. In order for a smartwatch or f...itness tracker to perform some simple feature, it is enough to say its name aloud.

— Voice assistant. In watches with voice assistant support, the level of user interaction with the device is displayed in a new qualitative way. The most popular virtual assistants are Google Assistant and Amazon Alexa. In Apple devices, the role of an assistant is performed by Apple Siri, in Samsung wearable gadgets — a virtual assistant Bixby. Unlike the voice control function, the assistant does not just turn on this or that feature, but allows you to perform certain operations in applications that require feedback.

— Sound signal. The ability to give sound signals using the built-in speaker. This feature will be useful primarily in situations where the gadget is not on hand — for example, if it is used as an alarm clock and is removed at night.

— Vibration. Vibration signal similar to that used in mobile phones. In wearable gadgets, such a signal is especially convenient due to the fact that the device is constantly in contact with the wearer's skin, so that the vibration is perfectly felt — and regardless of the level of noise around. In addition, vibration mode is also useful in quiet environments where a loud sound signal is undesirable.

— Built-in microphone. Own microphone built into the body of the device. Such equipment can be used for different purposes, depending on the type and features of the gadget. First of all, voice communication is impossible without a microphone. Another feature for which a microphone is required is the voice assistant (see above). And in children's smartwatches, it may be possible to remotely turn on the microphone from the parent gadget and listen to what is happening around the child; see the relevant paragraph below for details.

— Speakerphone(speaker). The ability to work the gadget in hands-free mode, using the built-in speaker and microphone for conversation. In a conventional smartwatch (see "Type"), this feature allows you to talk through the watch without removing the smartphone from your pocket; in watch-phones, speakerphone allows you to do so without headphones and headsets, and for children's smartwatches, this feature is almost mandatory. However the volume of the built-in speaker is usually low, so in a noisy environment its power may not be enough.

Types of sports and medical data collected by the gadget (plus some features of a similar purpose, such as sleep tracking, smart alarms, stress levels and women's calendar). Note that the features from this list can be found not only in specialized fitness trackers (see "Type"), but also in more traditional devices like smartwatches. Here are the most popular options:

— Pulse rate. Heart rate is one of the most important physiological parameters of a person. So that sports training is as effective as possible, the heart rate must be in a certain range (the specific value depends on the purpose of the training and the personal data of the user). And for some illnesses and treatments, a faster or slower heart rate can be an important signal, including a warning of danger.

— Pressure (tonometer). A sensor that measures the user's blood pressure. Note that the accuracy of such a sensor is usually quite low, the measurement error can be 10% or even more; so it will not replace a full-fledged medical tonometer. On the other hand, a gadget with this feature is quite capable of detecting a critical increase or decrease in pressure, which will allow you to take the necessary measures in a timely manner.

— ECG. A sen...sor that allows you to get detailed data about the work of the user's heart. Note that such a sensor is not a full-fledged electrocardiograph — in fact, it is an advanced type of heart rate monitor that can track the features of the heart rhythm. However, even this is enough to detect some dangerous phenomena — for example, atrial fibrillation, which at first is imperceptible to a person — and take appropriate measures in time.

— The blood oxygen. A sensor (the so-called pulse oximeter) that determines the saturation of the blood with oxygen (saturation); at the same time, the measurement is carried out by a non-invasive method — without punctures and other damage to the skin. Like most medical sensors in wearable gadgets, it is not accurate and is not a full-fledged medical device, but it is quite capable of responding to a critical decrease in the level of oxygen in the blood. It is believed that the presence of a pulse oximeter is relevant primarily for certain diseases, when saturation may decrease due to the disease itself or the characteristics of the treatment being taken. However, this feature can also be useful for quite healthy users who often travel at high altitudes — primarily climbers and aeronauts.

— Body temperature. The presence of a sensor for measuring temperature allows you to take measurements without the use of thermometers. Naturally, errors can occur, so a slight deviation from the norm may not be determined, but the device will easily fix a significant increase in temperature.

— T° of the environment. Even though smartwatches are worn on the body, the built-in sensors in them are usually designed to measure the ambient temperature. This information can be useful both for a general assessment of the surrounding conditions, and for specific purposes — in particular, weather forecasting. It is not uncommon for watches with this feature to also have a barometer (see "Navigation").

— Number of steps. The traditional pedometer is a feature for counting the number of steps taken by the user. These measurements usually use data from the accelerometer, and the results are quite accurate: most modern accelerometers are well calibrated and are quite capable of distinguishing tremors during steps from hand waves and other extraneous movements. The exception is trips in land transport: many wearable gadgets perceive shaking as steps, which should be taken into account when evaluating the results.

— Distance travelled. Measurement of the total distance traveled by the user. For this, either data from a pedometer or a GPS module are usually used (see "Navigation"); each option has its own merits. So, the pedometer is cheaper, it can be used even in rooms without windows, where the signal from satellites does not reach, and on simulators like treadmills, where the user does not move relative to the ground. GPS, in turn, gives higher accuracy, especially over long distances, and is not prone to false positives in vehicles. In some advanced gadgets, these methods can be combined — this is not cheap, but it allows you to combine the advantages of both options and achieve maximum accuracy.

— Movement speed. Determining the speed of the user's movement. As with distance travelled, measurement can be done in a variety of ways; see above for more details. Also note here that many gadgets with this feature are able not only to determine the current speed, but also to constantly record its value and display various indicators: the maximum achieved speed, the average value for training, etc.

— Energy spent (calories). Measurement of the number of calories burned by the user in the process of movement. These data are rather approximate, as they are calculated by indirect parameters (speed and range of movement, personal specs of a person, etc.). However, even this accuracy is quite enough to determine the overall effectiveness of training.

— The amount of fat burned. Measuring the amount of fat burned per workout. As in the case of calories (see above), the result of such measurements is quite approximate. However, in fact, absolute accuracy is not required, and fat loss data can be a powerful motivator.

— Activity time. A measurement of the total time during which the user is actively moving. In many models, such metering may provide additional options, such as fixing several periods of activity with breaks between them and determining the ratio between the time of movement and the time of rest.

— Smart alarm. An alarm clock that monitors the user's sleep phases and gives a signal to wake up at the optimal time for this. Human sleep consists of alternating phases, and waking up in the unfortunate phase creates a feeling of lethargy and fatigue, even if there was enough time to sleep. A smart alarm clock avoids such situations; its work is based on tracking the pulse, breathing rate and other parameters that differ depending on the phase of sleep. Note that the deviation of the signal from the set time can be up to half an hour, but this is usually a deviation towards an earlier rise. As a result, the risk of being late with a smart alarm clock is close to zero, and the lack of sleep time is compensated by the optimal moment of awakening.

— Sleep tracking. Sleep quality assessment is based on data from on-board sensors of fitness trackers or smartwatches. In particular, the heart rate monitor controls the number of contractions of the heart muscle, the accelerometer controls the user's movements. A blood oxygen sensor, if available on the wearable, improves the accuracy of sleep quality data collection. According to the readings of the sensors, the moments of entering and exiting the deep sleep phase are recorded. It is during this period that the restoration of the nervous system and the accumulation of energy for the coming day take place. In deep sleep, a person can completely reboot and gain strength, while in REM sleep, brain activity practically does not differ from the state of wakefulness. The sleep quality analysis feature helps you determine the best time to go to sleep and provides personalized recommendations to improve your night's sleep.

— The level of stress. The level of stress of the body allows you to evaluate the metric that determines the variability of the heartbeat — the difference in time between successive contractions of the heart muscle. Respiration rate, maximum oxygen consumption and excess oxygen consumption after exercise are also taken into account. The stress level score gives a clear picture of the user's experience during the day, however, the value of this parameter is in determining the most optimal body regimen for training. A high heart rate variability usually indicates you are in good shape for playing sports, while a low one can indicate fatigue, dehydration, or feeling unwell. All this directly affects the ability to train effectively. There are no clear units for measuring the level of stress — in smartwatches, the parameter is usually shown as a scale from 0 to 100, often indicating the number of hours the body is under stress and the time it takes to recover to a normal state.

— Women's calendar. The tool for tracking the menstrual cycle keeps abreast of the events of the expected dates of the menstrual period, allows you to determine the most favorable days for conception, helps to notice alarming symptoms in time and prevent many diseases in case of cycle disorders. Based on your total cycle length, the device calculates a predicted date for your next period. The women's calendar records cycle dates, fertility windows, and the day of ovulation. By adding your own notes to it, you can track fluctuations in sleep, appetite, fitness, mood changes and predict well-being for a particular day.

In addition to those described above, more specific types of measurements can be found in modern wearable gadgets.

The number of types of sports training supported by the smartwatch. The more of them, the wider the coverage of the potential audience is provided by a wearable gadget on the wrist.

The most common sports modes include running, walking, cycling, swimming, elliptical exercise, and so on. The quantity and quality of data for different sports depends on the technical level of equipment of a particular device. While some models only record heart rate and roughly calculate the number of calories burned, other smartwatches evaluate the effectiveness of a workout using a detailed list of data and even draw a conditional run track based on information from GPS satellites.

This block contains both various navigation systems ( GPS, Galileo) and auxiliary features for them ( aGPS, GPS tracking, maps, compass, altimeter , barometer). More about them:

— GPS module. GPS satellite navigation module built right into the watch/tracker. The initial purpose of such a module is to determine the current geographic coordinates; but how this information will be used depends on the specific type and model of the gadget. For example, in some devices GPS is used only for measuring the distance traveled and/or speed of movement, while more advanced models support full navigation and are equipped with built-in maps. In addition, this feature is almost mandatory in children's beacons (see "Type") — it is GPS that is responsible for determining the location of the child.

— aGPS. An auxiliary feature that allows you to speed up the start of the main GPS receiver. To work for its main purpose, such a receiver must update data on the location of navigation satellites; Obtaining this data in the classical way, directly from the satellites themselves, can take quite a long time (up to several minutes). This is especially true for the so-called "cold start" — when the receiver starts up after a long break in opera...tion, and the data stored in it has become completely outdated. aGPS (Assisted GPS) allows you to receive up-to-date service information from a mobile operator — from the nearest base station (this feature is supported by most operators nowadays). This can greatly speed up the startup process.

— GLONASS. This system is a Russian alternative to the American GPS. However it provides somewhat less accuracy, so GLONASS support is usually provided in addition to the GPS module. Simultaneous use of two systems, in turn, improves positioning accuracy.

— Galileo. European satellite navigation system, created as an alternative to the American GPS. Note that it is under the control of civilian departments, not the military. With a full fleet of 24 active satellites, the system gives an accuracy of up to 1 m in public mode and up to 20 cm with the GHA service. Working in conjunction with GPS, the Galileo system provides a more accurate position measurement, especially in densely populated areas.

— Maps. The feature of displaying topographic maps of the area with heights, relief and types of vegetation on the clock screen. Preinstalled maps are used for visual GPS navigation without being tied to a smartphone. Often, the ability to display maps is implemented in tactical smartwatches with a focus on tourism.

— GPS tracking. Many watches with the possibility of laying routes have the feature of guiding by the GPS track. At the same time, the wearable gadget acts as a navigator around the area, showing the route on the screen and suggesting where it is necessary to turn in one direction or another. Some smartwatches with a pronounced touristic bias also have a “Return Route” programme that allows you to go back along an already traveled route. In GPS tracker mode, trackpoints are usually recorded automatically based on the selected fixing interval. You can also mark a track point manually at any time.

— Compass. A classic compass is a device that indicates the direction to the cardinal points. Wearable gadgets usually use an electronic compass — a miniature magnetic sensor, the data from which, if necessary, are displayed on the display.

— Altimeter. A feature that allows you to determine the current altitude of the user's location. Note that the principle and format of the altimeter may be different. So, some models use barometer data for height measurements, others use information from a GPS sensor; the height itself can be determined relative to sea level, relative to some reference point, or in any of these ways, at the choice of the user. These details should be clarified separately.

— Barometer. A feature that allows you to determine the current atmospheric pressure. One of the applications of the barometer is weather forecasting: for example, a sharp drop in pressure usually signals the approach of bad weather. In addition, information from this sensor can be used to operate the altimeter (see above); and even if the gadget does not have an altimeter, the height difference between two points on the ground can be easily calculated from the pressure difference between them.

The size of the display installed in the gadget; for round screens, respectively, the diameter is indicated.

A larger screen, on the one hand, is more convenient to use, on the other hand, it significantly affects the dimensions of the entire device, which is especially critical for wearable gadgets. Therefore, manufacturers choose the display size in accordance with the purpose and functionality of each specific model — so that there is enough space on the screen and the device itself is not too bulky.

It is also worth mentioning that screens with a similar size may have different aspect ratios. For example, traditional smartwatches are usually equipped with square or round panels, while in fitness trackers, screens are often made elongated in height.

Screen size in dots (pixels) horizontally and vertically. In general, this is one of the indicators that determine the image quality: the higher the resolution, the clearer and smoother the picture on the screen (with the same size), the less noticeable are the individual dots. On the other hand, an increase in the number of pixels affects the cost of displays, their power consumption and requirements for a hardware platform (more powerful hardware is required, which itself will cost more). In addition, the specifics of using smartwatches is such that there is simply no need to install high-resolution screens in them. Therefore, modern wrist accessories use displays with a relatively low resolution: for example, 320x320 with a size of about 1.6" is considered quite sufficient even for premium watches.

The density of dots on the screen of the gadget, namely, the number of pixels that are on each inch of the panel vertically or horizontally.

The higher the PPI, the higher the detail of the screen, the clearer and smoother the image is. On the other hand, this indicator affects the price accordingly. Therefore, the higher the density of points, the more advanced, usually, this gadget is in terms of general capabilities. However, when choosing a screen, manufacturers take into account the general purpose and functionality of the device; so that even a small number of PPIs usually does not interfere with comfortable use.

The maximum brightness in nits that the screen of the device produces.

The high-brightness displays remain legible under intense ambient light, which is important for quickly retrieving information from the dial outdoors on a clear sunny day. However, a large margin for this parameter affects the cost and power consumption of the display, which reduces the battery life of a wearable device.

Bezel-less are displays in which the case or bezel does not occupy the usable area of the front panel, or it is minimized. In terms of design, bezels have both pros and cons. One of the most important reasons for adding substantial bezels to your screen is physical protection. The bezel-less display is very easy to scratch or damage when dropped. On the other hand, the frame takes up space on the screen, and this is one of the reasons why the frames in modern smartwatches are minimized, making the gadget more compact and stylish.