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CAT B35 4G Smartphone Review

Simply sturdy. The CAT B35 is a robust feature phone that has been designed for use in extreme environments. The device includes a 4G modem, but its apps selection is underwhelming. Read on to find out whether the CAT B35 is good enough for everyday use.

Modern smartphones are not designed for being used in dirty environments such as construction sites. Their large displays and numerous ports often make them vulnerable to breaking if they are dropped or accidentally submerged in liquids. By contrast, feature phones, better known as merely mobile phones or cell phones, are often less susceptible to breaking thanks to their smaller screens and more compact designs. Moreover, feature phones are usually less expensive than smartphones, so they are much cheaper to replace if something does go wrong. 

The CAT B35 has been designed to address the issues of using a smartphone in challenging environments with a rubber layer surrounding its frame, while all its connections are watertight. The physical keypad also makes the B35 easy to use with gloves on, which is often an issue with most smartphones that have large touchscreens.

We have chosen to compare the B35 against the CAT S31, the CUBOT King Kong, the Elephone Soldier and the Doogee S55 to determine whether the latest CAT device to grace our office is an excellent alternative to the other budget outdoor smartphones that are currently on the market.

Qualcomm 205 2 x 1.1 GHz, Cortex-A7
Graphics adapter
512 MB 
2.40 inch 4:3, 320 x 240 pixel 167 PPI, glossy: yes
4 GB Flash, 4 GB 
, 1 GB free
1 USB 2.0, Audio Connections: 3.5 mm headphone jack, Card Reader: up to 32 GB microSD cards
802.11 b/g/n (b/g/n = Wi-Fi 4/), Bluetooth 4.1, 2G: 850, 900, 1,800, 1,900 MHz. 3G: B1, B2, B5, B8. 4G: B1, B3, B7, B8, B20, Dual SIM, LTE, GPS
height x width x depth (in mm): 13.9 x 138 x 60 ( = 0.55 x 5.43 x 2.36 in)
8.7 Wh, 2300 mAh Lithium-Ion
Primary Camera: 2 MPix
Additional features
Speakers: Mono speaker on the back of the device, Keyboard: Physical keypad, Keyboard Light: yes, Charger, USB cable, KaiOS, 24 Months Warranty, LTE Cat 4: Download – 150 Mbps; Upload - 50Mbps. SAR value: 1.88 W/kg, IP68 certified, MIL-STD-810G certified, Flashlight, FM radio, fanless, ruggedized
130 g ( = 4.59 oz / 0.29 pounds), Power Supply: 61 g ( = 2.15 oz / 0.13 pounds)
109 Euro
Note: The manufacturer may use components from different suppliers including display panels, drives or memory sticks with similar specifications.



The B35 is a practical looking feature phone and does not incorporate any novel sliding mechanisms that other feature phones such as the Nokia 8110 have. The outer shell is made from a rubbery plastic and has several horizontal grooves that help make the device feel grippy in hand. However, the texture is too slippery for our tastes and we would have preferred CAT to have chosen an even grippier case material given the scenarios in which the B35 will primarily be used.

The B35 is 13.9 millimetres (~0.55 in) thick, which puts it on par with other rugged smartphones. Overall, our test device fits well in our hands thanks to its rounded corners.

The case is IP68 certified, which means that the B35 is dustproof and can be submerged in up to at least 1 metre (~3 ft) of water. The device is only IP68 rated for when its rubber covers are sealed though, so the B35 is not waterproof, dustproof or water resistant when it is being charged, for example. Moreover, the rubbers are tough to remove, which should indicate that the covers will stay in place for a long time. We would recommend opening the SIM card tray with tools too, as you may break off a fingernail if you use your hands.

Caterpillar Inc also states that the B35 should survive drops of up to 1.8 metres (~5.9 ft) onto concrete. We did not test the validity of this statement, but the thick protruding edges that surround the display give us the impression that they would protect the screen if the device were dropped display down.


Size Comparison

138 mm / 5.43 inch 60 mm / 2.36 inch 13.9 mm / 0.547 inch 130 g0.2866 lbs148 mm / 5.83 inch 105 mm / 4.13 inch 1 mm / 0.03937 inch 1.5 g0.00331 lbs


The B35 has less storage and RAM than even the cheapest of smartphones. The B35 has 512 MB of RAM and 4 GB of internal storage, which reminds us of old Android smartphones such as the HTC Desire or the Samsung Galaxy. Our test device had just 1 GB of free internal storage when we first switched it on, but fortunately it supports up to 32 GB microSD cards for additional storage. CAT sells the B35 in single or dual-SIM variants, although the dual-SIM variant is the only model currently available in Central Europe. Additionally, the card slot has only two spaces, so the CAT B35 is limited to using either a single nano SIM and a microSD card or two nano SIM cards. The B35 currently costs between €80 and €100 (~$90/$113).


The B35 comes with KaiOS pre-installed, which we have seen in other feature phones such as the Nokia 8110. The OS is reasonably easy to use and operates like other feature phone OS’ from the early 2000s. Our test device comes with a few apps pre-installed such as the Google Assistant, Google Maps, Google Search and YouTube. There is an app store too, but there are no messaging apps such as Signal, Threema or WhatsApp, which feels like a missed opportunity. However, KaiOS allows account holders to remotely lock or block their devices if they are lost or stolen, which is a useful and practical feature.

Communication & GPS

The B35 supports the bare minimum of Wi-Fi and LTE connectivity. The device supports IEEE 802.11 b/g/n standards and connects to 2.4 GHz networks, which means that the B35 cannot take advantage of fast ac Wi-Fi or 5 GHz networks. The B35 also supports enough LTE frequencies for using the device in Europe, but you may struggle to connect to an LTE network outside of that area.

We found web browsing an unpleasant experience on our test device. Websites load considerably slower on the B35 than they do even on the cheapest smartphones, while the display is too small for extensive web browsing. We would only recommend using the B35 to browse the web as a stopgap until you can use a device with faster Wi-Fi and a larger display.

The LTE reception is good in built-up areas though. Our test device maintained at least half signal strength when we were using the device inside buildings, which is good enough for daily use.

The B35 has a GPS module and has Google Maps pre-installed too, so it could be used for basic navigation tasks. Our test device found our location during our tests, but it takes over a minute to do so.  Unfortunately, we could not use any navigation features, but we were able to view routes, which is somewhat useful.

Telephone Features & Call Quality

The CAT B35 supports voice over LTE (VoLTE), but the carrier must have provisioned the device for VoLTE to work. A nice touch of feature phones is the ease with which you can make calls. We can start dialling a number directly from the home screen and press the green call button to start a call, which is a more straightforward experience than on many modern smartphones. Our test device has decent call quality too. 

Contacts can be imported from Google, Outlook or from a microSD card.


The B35 has a poor camera. CAT has equipped the device with a single 2 MP rear-facing sensor, which takes photos that lack detail and are dominated by image noise. The camera can take shots in low-light too, but the results are predictably grainy and unimpressive. We have hardly anything positive to write about the camera, but selfie fans will be especially disappointed as there is no front-facing camera.

The rear-facing camera can record videos in up to 720p, while the sensor even reacts to changes in ambient light. Our test device reproduces audio relatively well too, but the microphone picks up noises from moving the device during a video recording, which is frustrating.

Image Comparison

Choose a scene and navigate within the first image. One click changes the position on touchscreens. One click on the zoomed-in image opens the original in a new window. The first image shows the scaled photograph of the test device.

Scene 1Scene 2Scene 3
click to load images

Accessories & Warranty

Our test device came with a charger and a USB cable. CAT does not sell any B35-specific accessories on its website, although it does sell generic CAT-branded accessories such as the “Active Signature Leather Phone Holster”, which currently costs $79.99.

The B35 comes with 24 months manufacturer’s warranty. Please see our Guarantees, Return policies and Warranties article for country-specific information.

Input Devices & Operation

Using the B35 may take some getting used to if you are used to a modern smartphone. There is no touchscreen, so you can only enter text using the numeric keys. Frustratingly, the button combinations are inconsistent between apps. In Google Maps we must first tap the number key and then select the desired letter by using the arrow keys, while other apps use the more traditional function of tapping the same number key multiple times to cycle through letters assigned to that key.

CAT has included three quick-access buttons on the home screen that act as shortcuts for going to saved contacts, for example. The green call key also doubles as a shortcut to quickly view your last dialled numbers. Moreover, the red end call button serves as a back button when you are not on a call. Overall, the B35 is easy to use, although it has its quirks.

It is also pleasing that the keys have a clear pressure point. However, the buttons are too small to be used with gloves for our liking.


Sub-pixel array
Sub-pixel array

The B35 has a 2.4-inch display that operates at a native 320 x 240 resolution. The resolution is too low in our opinion, as we can see individual pixels without looking closely. The display reaches a maximum brightness of 490 cd/m² according to X-Rite i1Pro 2, which is on par with cheap outdoor phones. By contrast, the CAT S31 has a much brighter display, which makes it easier to use in bright ambient light. Our test device also has a shockingly high black value, which we measure at 6 cd/m². The black value is much higher than what our comparison devices achieve and results in an abysmal 84:1 contrast ratio. In short, black tones look grey, and colour gradients look like one homogenous block of colour.

Distribution of brightness
tested with X-Rite i1Pro 2
Maximum: 490 cd/m² (Nits)
Contrast: 84:1 (Black: 5.8 cd/m²)
320x240, 2.40
Cubot King Kong
IPS, 1280x720, 5.00
Doogee S55
IPS, 1440x720, 5.50
Elephone Soldier
IPS, 2560x1440, 5.50
IPS, 1280x720, 4.70
Nokia 8110 4G
TFT, 320x240, 2.45
Brightness middle
Black Level *
Brightness Distribution
Colorchecker dE 2000 *
Colorchecker dE 2000 max. *
Greyscale dE 2000 *
2.26 97%
1.87 118%
2.16 102%
2.49 88%
2.43 91%
7244 90%
7606 85%
6971 93%
7175 91%
17884 36%

* ... smaller is better

Screen Flickering / PWM (Pulse-Width Modulation)

To dim the screen, some notebooks will simply cycle the backlight on and off in rapid succession - a method called Pulse Width Modulation (PWM) . This cycling frequency should ideally be undetectable to the human eye. If said frequency is too low, users with sensitive eyes may experience strain or headaches or even notice the flickering altogether.
Screen flickering / PWM detected 9091 Hz

The display backlight flickers at 9091 Hz (Likely utilizing PWM) .

The frequency of 9091 Hz is quite high, so most users sensitive to PWM should not notice any flickering.

In comparison: 53 % of all tested devices do not use PWM to dim the display. If PWM was detected, an average of 18683 (minimum: 5 - maximum: 3846000) Hz was measured.

Our test device uses pulse-width modulation (PWM) to regulate display brightness, which can cause eye strain and headaches for some people. We measure the PWM frequency at 9,091 Hz, which should be high enough to not cause issues for even those who are PWM sensitive. We cannot guarantee this though, so please bear in mind that the B35 uses PWM if you are considering the device and you are PWM sensitive.

Our test device is usable outside on overcast days, but we struggled to read the display on sunny days as reflections often obscured the screen. The B35 has poor viewing angles too with noticeable colour shifts even at obtuse angles.

Using the CAT B35 outside
Using the CAT B35 outside
Viewing Angles
Viewing Angles


The B35 has limited performance, as we noticed when using the pre-installed web browser. The little RAM and the slow Qualcomm 205 SoC combine to provide lowly system performance. Cycling through menus usually feels smooth, while YouTube videos typically play without any lagging or jerking. Even scrolling on Google Maps works well. Some apps would occasionally refuse to load though, and there have been reports online of some B35 devices frequently crashing. We experienced no such issues during our tests though.

In short, the B35 is powerful enough for its purposes, but its performance is much lower than that of comparably priced smartphones.


KaiOS does not include any complex 3D games such as those on the Google Play Store, but the B35 could not play them anyway. There are a few simple 2D titles such as platformers, puzzle games or top-down racing games. At the time of writing the KaiOS app store has around 20 games, which is incomparable to the thousands on the Play Store.

Most games play smoothly and load quickly on our test device. The graphics requirements are basic though, so it is not an impressive feat.



Our test device hardly heats up even when we subjected it to sustained load.

Max. Load
 28.7 °C
84 F
33.3 °C
92 F
28.7 °C
84 F
 28.8 °C
84 F
32.2 °C
90 F
28.6 °C
83 F
 28.7 °C
84 F
30.5 °C
87 F
28.4 °C
83 F
Maximum: 33.3 °C = 92 F
Average: 29.8 °C = 86 F
28.8 °C
84 F
29.3 °C
85 F
28.1 °C
83 F
28.9 °C
84 F
28.8 °C
84 F
27.8 °C
82 F
29.1 °C
84 F
29.8 °C
86 F
27.7 °C
82 F
Maximum: 29.8 °C = 86 F
Average: 28.7 °C = 84 F
Power Supply (max.)  38.8 °C = 102 F | Room Temperature 21.2 °C = 70 F | Voltcraft IR-260
(+) The average temperature for the upper side under maximal load is 29.8 °C / 86 F, compared to the average of 32.7 °C / 91 F for the devices in the class Smartphone.
(+) The maximum temperature on the upper side is 33.3 °C / 92 F, compared to the average of 35 °C / 95 F, ranging from 21.9 to 56 °C for the class Smartphone.
(+) The bottom heats up to a maximum of 29.8 °C / 86 F, compared to the average of 33.8 °C / 93 F
(+) In idle usage, the average temperature for the upper side is 28.3 °C / 83 F, compared to the device average of 32.7 °C / 91 F.


Pink Noise speaker test
Pink Noise speaker test

The B35 has a speaker that sits on the rear of the device. The frequency range is dominated by high tones, particularly at high volumes. However, the audio quality is good enough at medium volumes to occasionally listen to a song. In short, the speaker will fill a small room and is on par with the speakers in other cheap smartphones.

The B35 has a headphone jack and supports Bluetooth audio. Both outputs transmit audio cleanly.

dB(A) 0102030405060708090Deep BassMiddle BassHigh BassLower RangeMidsHigher MidsLower HighsMid HighsUpper HighsSuper Highs2041.442.42541.746.63139.149.34035.335.65033.832.66332.927.88027.828.210028.328.512522.127.916021.934.420019.645.425020.248.631519.455.540017.765.350016.86963016.170.2800167510001578.7125016.377.116001575.9200014.473.825001475.831501477.2400013.879.8500013.981.8630013.769.6800013.958.31000013.953.61250013.957.61600013.971.7SPL70.827.388.5N24.90.974median 16median 69median 81.2Delta4.7167.240.740.53537.635.637.233.128.43430.632.328.519.823.519.222.617.821.914.121.714.82512.630.311.339.210.847.610.252.79.459.1964.18.364.78.363.28.262.6861.98.162.3863.7864.77.964.6860.88.353.48.349.78.343.78.326.868.32174.421.60.331.4median 8.3median 52.7median 52.94.717.221.5hearing rangehide median Pink NoiseCAT B35Cubot King Kong
Frequency diagram (checkboxes can be checked and unchecked to compare devices)
CAT B35 audio analysis

(+) | speakers can play relatively loud (88.5 dB)
Bass 100 - 315 Hz
(-) | nearly no bass - on average 81.2% lower than median
(+) | bass is linear (0% delta to prev. frequency)
Mids 400 - 2000 Hz
(-) | nearly no mids - on average 81.2% lower than median
(+) | mids are linear (0% delta to prev. frequency)
Highs 2 - 16 kHz
(-) | nearly no highs - on average 81.2% lower than median
(+) | highs are linear (0% delta to prev. frequency)
Overall 100 - 16.000 Hz
(-) | overall sound is not linear (115.5% difference to median)
Compared to same class
» 84% of all tested devices in this class were better, 5% similar, 11% worse
» The best had a delta of 12%, average was 38%, worst was 134%
Compared to all devices tested
» 95% of all tested devices were better, 2% similar, 3% worse
» The best had a delta of 4%, average was 26%, worst was 134%

Cubot King Kong audio analysis

(±) | speaker loudness is average but good (74.4 dB)
Bass 100 - 315 Hz
(-) | nearly no bass - on average 52.9% lower than median
(+) | bass is linear (0% delta to prev. frequency)
Mids 400 - 2000 Hz
(-) | nearly no mids - on average 52.9% lower than median
(+) | mids are linear (0% delta to prev. frequency)
Highs 2 - 16 kHz
(-) | nearly no highs - on average 52.9% lower than median
(+) | highs are linear (0% delta to prev. frequency)
Overall 100 - 16.000 Hz
(-) | overall sound is not linear (113.1% difference to median)
Compared to same class
» 84% of all tested devices in this class were better, 2% similar, 14% worse
» The best had a delta of 12%, average was 38%, worst was 134%
Compared to all devices tested
» 95% of all tested devices were better, 1% similar, 4% worse
» The best had a delta of 4%, average was 26%, worst was 134%

Power Management

Power Consumption

The B35 is a comparatively efficient smartphone and consumes a lot less than our comparison devices. We did expect this though as the device is noticeably weaker and has a smaller display than any of the devices in our comparison table.

Power Consumption
Off / Standbydarklight 0 / 0.1 Watt
Idledarkmidlight 0.6 / 0.9 / 1.1 Watt
Load midlight 1.7 / 1.9 Watt
 color bar
Key: min: dark, med: mid, max: light        Metrahit Energy
Currently we use the Metrahit Energy, a professional single phase power quality and energy measurement digital multimeter, for our measurements. Find out more about it here. All of our test methods can be found here.
2300 mAh
Doogee S55
5500 mAh
Elephone Soldier
5000 mAh
Cubot King Kong
4400 mAh
4000 mAh
Average Qualcomm 205
Average of class Smartphone
Power Consumption
Idle Minimum *
0.565 ?(0.53 - 0.6, n=2)
0.89 ?(0.44 - 2.37, n=155, last 2 years)
Idle Average *
0.835 ?(0.77 - 0.9, n=2)
1.464 ?(0.69 - 4.26, n=155, last 2 years)
Idle Maximum *
0.95 ?(0.8 - 1.1, n=2)
1.669 ?(0.79 - 4.45, n=155, last 2 years)
Load Average *
1.595 ?(1.49 - 1.7, n=2)
4.84 ?(2.4 - 15.3, n=155, last 2 years)
Load Maximum *
1.815 ?(1.73 - 1.9, n=2)
7.71 ?(3.85 - 17.8, n=155, last 2 years)

* ... smaller is better

Battery Life

CAT boasts on its website that the B35 will last up to 30 days on standby, which is something that we did not have the time to test during our time with our test device. However, its 2,300 mAh battery does deliver decent battery life. Our test device lasted for 10:35 hours in our Wi-Fi battery life test, which is 23% longer than what the Nokia 8110 achieved in the same test with its 1,500 mAh battery. The days of phones lasting for days on a single charge are long gone because of colour displays and more complex communication modules, but the B35 should last a few days if used sparingly. We reckon some people could even eke out a week between charges if they regularly switch off the Wi-Fi and rarely make calls.

Frustratingly, the B35 takes between 2-3 hours to recharge fully with the included charger. The battery is not replaceable either, so you will be chained to a power bank or mains outlet for a few hours if you must recharge your device completely.

Battery Runtime
WiFi Websurfing
10h 35min
2300 mAh
Doogee S55
5500 mAh
Elephone Soldier
5000 mAh
Cubot King Kong
4400 mAh
4000 mAh
Nokia 8110 4G
1500 mAh
Battery Runtime
WiFi v1.3


+ GPS available
+ 4G with VoLTE
+ Dual-SIM
+ microSD slot
+ good call quality
+ bright screen
+ relatively cool surface temperatures
+ loud mono speaker
+ robust case


- limited performance
- internet browsing is tricky
- the battery is not user replaceable
- disappointing camera
- limited storage


The CAT B35 Smartphone Review. Test device courtesy of CAT Germany.
The CAT B35 Smartphone Review. Test device courtesy of CAT Germany.

The CAT B35 is a budget feature phone that is drop, dust and water resistant with basic communication capabilities such as 4G and Wi-Fi. One should be aware of the pros and cons of using a feature phone in 2018 as the experience is noticeably different from using a modern smartphone. The B35 has a decent battery life, while its compact size and physical keypad are useful, but its camera and display are dreadful.

Moreover, KaiOS feels outdated compared to Android or iOS and browsing the web is a chore on such a small screen. Some functions such as volume controls are poorly thought out too and inputting letters is not a consistent experience across all apps.

The CAT B35 is a solid choice for those who are mobile purists and regularly travel to or work in harsh environments. 

However, the CAT B35 may be a suitable device if you do not care for having a flashy smartphone and rarely use phones to browse the internet. In short, the B35 is a rugged feature phone that will last for days on a single charge and can be used in places such as construction sites without any issues. 

CAT B35 - 12/17/2018 v6(old)
Florian Schmitt

Games Performance
3 / 70 → 4%
Application Performance
94 / 91 → 100%
Smartphone - Weighted Average


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Florian Schmitt, 2018-12-18 (Update: 2019-02-23)