Difference between revisions of "R.35 (SA38)"

From War Thunder Wiki
Jump to: navigation, search
m (Undo revision 16194 by U28580205 (talk)br is up to date)
(Updated template w/ new design, Moved texts around to appropriate sections)
Line 2: Line 2:
  
 
== Description ==
 
== Description ==
<!--''In the description, the first part needs to be about the history of the creation and combat usage of the vehicle, as well as its key features. In the second part, tell the reader about the ground vehicle in the game. Insert the screenshot of the vehicle. If the novice player does not remember the vehicle by name, they will immediately understand what kind of vehicle it is talking about.''-->
+
<!--''In the description, the first part should be about the history of the creation and combat usage of the vehicle, as well as its key features. In the second part, tell the reader about the ground vehicle in the game. Insert a screenshot of the vehicle, so that if the novice player does not remember the vehicle by name, he will immediately understand what kind of vehicle the article is talking about.''-->
 
[[File:GarageImage_{{PAGENAME}}.jpg|420px|thumb|left]]
 
[[File:GarageImage_{{PAGENAME}}.jpg|420px|thumb|left]]
 
{{break}}
 
{{break}}
 
The '''{{specs|name}}''' (Light support tank 1939 R) is a Rank {{specs|rank}} French light tank {{Battle-rating|1}}. It was introduced in [[Update 1.75 "La Résistance"]]. Although it is a "light tank", the R.39 feels pretty cumbersome in every way: slow reload speed, low max speed and bad acceleration. It actually feels more like an heavy tank...without the benefits of heavy armour. This tank's design is very reminiscent of other rank 1 French tanks, hence, players should be used to a subpar gun, "heavy" armour and low mobility.  
 
The '''{{specs|name}}''' (Light support tank 1939 R) is a Rank {{specs|rank}} French light tank {{Battle-rating|1}}. It was introduced in [[Update 1.75 "La Résistance"]]. Although it is a "light tank", the R.39 feels pretty cumbersome in every way: slow reload speed, low max speed and bad acceleration. It actually feels more like an heavy tank...without the benefits of heavy armour. This tank's design is very reminiscent of other rank 1 French tanks, hence, players should be used to a subpar gun, "heavy" armour and low mobility.  
  
 +
== General info ==
 +
=== Survivability and armour ===
 +
<!--''Describe armour protection. Note the most well protected and key weak areas. Appreciate the layout of modules as well as the number and location of crew members. Is the level of armour protection sufficient, is the placement of modules helpful for survival in combat?''
 +
 +
''If necessary use a visual template to indicate the most secure and weak zones of the armour.''-->
 
With good armour thickness and surprising hull angles, this tank can take some beating at a distance, provided you do not get a lucky shot in the turret ring or that you face a heavy-hitting gun. This should get you into effective combat ranges (500 - m) in relative safety. The most obvious weakspot is its turret flat left side, which is only 45 mm thick and badly angled, this makes hull-down position ineffective.
 
With good armour thickness and surprising hull angles, this tank can take some beating at a distance, provided you do not get a lucky shot in the turret ring or that you face a heavy-hitting gun. This should get you into effective combat ranges (500 - m) in relative safety. The most obvious weakspot is its turret flat left side, which is only 45 mm thick and badly angled, this makes hull-down position ineffective.
  
Line 13: Line 18:
 
In an ambush position, this tank could face its opponents backwards (engine deck first). This unusual tactic could confuse enemies for a moment and provide extra protection as your engine may absorb shots. This will also decrease the chances of a lucky penetration : if turret is facing enemy, almost 90% of exposed surfaces have ~60 + mm of LoS thickness. If danger gets too high, you could give it the gas and "fly" away in forward motion.
 
In an ambush position, this tank could face its opponents backwards (engine deck first). This unusual tactic could confuse enemies for a moment and provide extra protection as your engine may absorb shots. This will also decrease the chances of a lucky penetration : if turret is facing enemy, almost 90% of exposed surfaces have ~60 + mm of LoS thickness. If danger gets too high, you could give it the gas and "fly" away in forward motion.
  
The 37 mm is not the best gun, but it can actually do some damage at reasonable ranges. Bear in mind its long reload time (for the BR)and back up into cover between shots. One should be an experimented tanker in order to use the most out of this gun as its post-penetration damage is poor: snipe crew members and modules one at a time. Avoid being too close to the front line  as your slow reload speed makes multi-target engagement difficult. Your turret slewing rate is also an issue since you'll not be able to react in time to flanking opponents.
 
 
The mobility is this tank's biggest weakness: while it does not like long-range engagements and needs to close-up with its foes in order to damage them, its very low speed will always leave it far behind its allies. With its narrow tracks and poor power ratio (8.09 HP/ton), the R.39 hates being taken out in the mud as its speeds fall drastically. 20 km/h forward and -3 km/h backwards is all you'll get from this struggling 73 HP engine. Plan your moves in advance and do not stay too near to the front line as a successful retreat is hard to achieve with such a slow tank.
 
 
== General info ==
 
=== Survivability and armour ===
 
<!--''Describe armour protection. Note the most well protected and key weak areas. Appreciate the layout of modules as well as the number and location of crew members. Is the level of armour protection sufficient, is the placement of modules helpfull for survival in combat?''
 
 
''If necessary use a visual template to indicate the most secure and weak zones of the armour.''-->
 
 
'''Armour type:'''
 
'''Armour type:'''
 
* Cast homogeneous armour
 
* Cast homogeneous armour
Line 28: Line 24:
 
! Armour !! Front (Slope angle) !! Sides !! Rear !! Roof
 
! Armour !! Front (Slope angle) !! Sides !! Rear !! Roof
 
|-
 
|-
| Hull || 32 mm (13-64°) ''Front plate'' <br> 22 mm (73-74°), 32 mm (24-26°) ''Front glacis'' <br> 32 mm (0-74°) ''Lower glacis'' <br> 32 mm (23°) ''Driver’s plate'' || 40 mm (1-33°) <br> 40 mm (1-2°) || 40 mm (24-30°) ''Top'' <br> 40 mm (9-32°) ''Bottom'' || 25 mm <br> 5 mm ''Engine grille''
+
| Hull || 32 mm (13-64°) ''Front plate'' <br> 22 mm (73-74°), 32 mm (24-26°) ''Front glacis'' <br> 32 mm (0-74°) ''Lower glacis'' <br> 32 mm (23°) ''Driver’s plate'' || 40 mm (1-33°) <br> 40 mm (1-2°) || 40 mm (24-30°) ''Top'' <br> 40 mm (9-32°) ''Bottom'' || 25 mm <br> 5 mm ''Engine grille''
 
|-
 
|-
| Turret || 45 + 25 mm (5°) ''Turret front'' <br> 45 mm (28-30°) ''Left side'' <br> 25 mm (10-19°) ''Gun mantlet'' || 40 mm (1-27°) || 40 mm (8-63°) || 25 mm
+
| Turret || 45 + 25 mm (5°) ''Turret front'' <br> 45 mm (28-30°) ''Left side'' <br> 25 mm (10-19°) ''Gun mantlet'' || 40 mm (1-27°) || 40 mm (8-63°) || 25 mm
 
|-
 
|-
 
! Armour !! Sides !! Roof  
 
! Armour !! Sides !! Roof  
Line 40: Line 36:
  
 
=== Mobility ===
 
=== Mobility ===
<!--''Write about the mobility of the ground vehicle. Estimate the specific power and maneuverability as well as the maximum speed forward and backward.''-->
+
<!--''Write about the mobility of the ground vehicle. Estimate the specific power and manoeuvrability, as well as the maximum speed forwards and backwards.''-->
 +
The mobility is this tank's biggest weakness: while it does not like long-range engagements and needs to close-up with its foes in order to damage them, its very low speed will always leave it far behind its allies. With its narrow tracks and poor power ratio (8.09 HP/ton), the R.39 hates being taken out in the mud as its speeds fall drastically. 20 km/h forward and -3 km/h backwards is all you'll get from this struggling 73 HP engine. Plan your moves in advance and do not stay too near to the front line as a successful retreat is hard to achieve with such a slow tank.
 +
 
 
{| class="wikitable" style="text-align:center"
 
{| class="wikitable" style="text-align:center"
 
|-
 
|-
Line 85: Line 83:
 
== Armaments ==
 
== Armaments ==
 
=== Main armament ===
 
=== Main armament ===
<!--''Give the reader information about the characteristics of the main gun. Assess its effectiveness in a battle based on the reloading speed, ballistics and the power of shells. Do not forget about the flexibilty of the fire, that is how quickly the cannon can be aimed at the target, open fire on it and aim at another enemy. Add a link to the main article on the gun: <code><nowiki>{{main|Name of the weapon}}</nowiki></code>. Describe in general terms the ammunition available for the main gun. Give advice on how to use them and how to fill the ammunition storage.''-->
+
<!--''Give the reader information about the characteristics of the main gun. Assess its effectiveness in a battle based on the reloading speed, ballistics and the power of shells. Do not forget about the flexibility of the fire, that is how quickly the cannon can be aimed at the target, open fire on it and aim at another enemy. Add a link to the main article on the gun: <code><nowiki>{{main|Name of the weapon}}</nowiki></code>. Describe in general terms the ammunition available for the main gun. Give advice on how to use them and how to fill the ammunition storage.''-->
 
{{main|SA38 L/33 (37 mm)}}
 
{{main|SA38 L/33 (37 mm)}}
 +
 +
The 37 mm is not the best gun, but it can actually do some damage at reasonable ranges. Bear in mind its long reload time (for the BR) and back up into cover between shots. One should be an experimented tanker in order to use the most out of this gun as its post-penetration damage is poor: snipe crew members and modules one at a time. Avoid being too close to the front line as your slow reload speed makes multi-target engagement difficult. Your turret slewing rate is also an issue since you'll not be able to react in time to flanking opponents.
  
 
{| class="wikitable" style="text-align:center"
 
{| class="wikitable" style="text-align:center"
Line 129: Line 129:
 
! rowspan="2" data-sort-type="text" | Ammunition
 
! rowspan="2" data-sort-type="text" | Ammunition
 
! rowspan="2" class="unsortable" | Type of <br /> warhead
 
! rowspan="2" class="unsortable" | Type of <br /> warhead
! colspan="6" | '''Penetration''' '''''in mm''''' '''@ 90°'''
+
! colspan="6" | '''Penetration''' '''''in mm''''' '''@ 0° Angle of Attack'''
 
|-
 
|-
 
! 10m
 
! 10m
Line 178: Line 178:
  
 
=== Machine guns ===
 
=== Machine guns ===
<!--''Offensive and anti-aircraft machine guns not only allow you to fight some aircraft, but also are effective against lightly armoured vehicles. Evaluate machine guns and give recommendations on its use.''-->
+
<!--''Offensive and anti-aircraft machine guns not only allow you to fight some aircraft but also are effective against lightly armoured vehicles. Evaluate machine guns and give recommendations on its use.''-->
 
{{main|MAC 31 (7.5 mm)}}
 
{{main|MAC 31 (7.5 mm)}}
  
Line 196: Line 196:
 
|}
 
|}
  
== Usage in the battles ==
+
== Usage in battles ==
<!--''Describe the tactics of playing in the vehicle, the features of using vehicles in the team and advice on tactics. Refrain from creating a "guide" - do not impose a single point of view but give the reader food for thought. Describe the most dangerous enemies and give recommendations on fighting them. If necessary, note the specifics of the game in different modes (AB, RB, SB).''-->
+
<!--''Describe the tactics of playing in the vehicle, the features of using vehicles in the team and advice on tactics. Refrain from creating a "guide" - do not impose a single point of view but instead give the reader food for thought. Describe the most dangerous enemies and give recommendations on fighting them. If necessary, note the specifics of the game in different modes (AB, RB, SB).''-->
 
As with any French rank 1 vehicle, follow your allies and effectively be a ''support'' tank. With your low max speed, your role is very limited in the battlefield and resumes as such: stick to the frontline and try to avoid being shot at.  
 
As with any French rank 1 vehicle, follow your allies and effectively be a ''support'' tank. With your low max speed, your role is very limited in the battlefield and resumes as such: stick to the frontline and try to avoid being shot at.  
  
Line 209: Line 209:
  
 
=== Pros and cons ===
 
=== Pros and cons ===
<!--''Summarize and briefly evaluate the vehicle in terms of its characteristics and combat effectiveness. Mark its pros and cons in a bulleted list. Do not use more than 6 points for each of the characteristics. Avoid using categorical definitions such as "bad", "good" and the like - they have a substitution in the form of softer "inadequate", "effective".''-->
+
<!--''Summarize and briefly evaluate the vehicle in terms of its characteristics and combat effectiveness. Mark its pros and cons in a bulleted list. Try not to use more than 6 points for each of the characteristics. Avoid using categorical definitions such as "bad", "good" and the like - use substitutions with softer forms such as "inadequate" and "effective".''-->
 
'''Pros:'''
 
'''Pros:'''
* Tiny profile
+
* Tiny profile = tiny tank
* Tiny tank
 
 
* Has one of the best French gun at rank 1
 
* Has one of the best French gun at rank 1
 
* Has decent sloped hull armour
 
* Has decent sloped hull armour
 
* Has a very thick gun mantlet area: 10mm gun shield + 45 mm armour + 20 mm internal shield.
 
* Has a very thick gun mantlet area: 10mm gun shield + 45 mm armour + 20 mm internal shield.
 
* Thick sides allows for heavy angling
 
* Thick sides allows for heavy angling
* MAC 31 coaxial MG
 
 
'''Cons:'''
 
'''Cons:'''
* Only one choice of ammunition.
+
* Only one choice of ammunition, that one choice also has no explosive filler
* That one choice has no explosive filler
 
 
* Only two crew members, one knocked out means tank destroyed.
 
* Only two crew members, one knocked out means tank destroyed.
* Extremely low speed
+
* Extremely low speed, with bad cross-country and hill-climbing ability
 
* Thin turret ring
 
* Thin turret ring
 
* Slow reload speed
 
* Slow reload speed
 
* Only 2 crew members in a cramped position (easy to one-shot)
 
* Only 2 crew members in a cramped position (easy to one-shot)
* Bad cross-country and hill-climbing ability
 
 
* Awful reverse speed of -3 km/h
 
* Awful reverse speed of -3 km/h
  
 
== History ==
 
== History ==
<!--''Describe the history of the creation and combat usage of the ground vehicle in more detail than in the introduction. If the historical reference turns out to be too big, take it to a separate article, taking a link to an article about the vehicle and adding a block "/historical reference" (example: https://wiki.warthunder.com/Name-vehicles/historical reference) and add a link to it here using the <code>main</code> template. Be sure to include links to sources at the end of the article.''-->
+
''Describe the history of the creation and combat usage of the ground vehicle in more detail than in the introduction. If the historical reference turns out to be too big, take it to a separate article, taking a link to the article about the vehicle and adding a block "/ History" (example: <nowiki>https://wiki.warthunder.com/(Vehicle-name)/History</nowiki>) and add a link to it here using the <code>main</code> template. Be sure to reference text and sources by using <code><nowiki><ref></nowiki></code>, as well as adding them at the end of the article. This section may also include the vehicle's dev blog entry (if applicable) and the in-game encyclopedia description (under <code><nowiki>=== Encyclopedia Info ===</nowiki></code>, also if applicable).''
  
 
== Media ==
 
== Media ==
''An excellent addition to the article will be video guides, as well as screenshots from the game and photos.''
+
''Excellent additions to the article would be video guides, screenshots from the game, and photos.''
  
== Read also ==
+
== See also ==
''Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example,''
+
''Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:''
 
* ''reference to the series of the vehicles;''
 
* ''reference to the series of the vehicles;''
 
* ''links to approximate analogues of other nations and research trees.''
 
* ''links to approximate analogues of other nations and research trees.''
''ETC.''
 
  
== Sources ==
+
== External links ==
 
''Paste links to sources and external resources, such as:''
 
''Paste links to sources and external resources, such as:''
 
* ''topic on the official game forum;''
 
* ''topic on the official game forum;''
 +
* ''encyclopedia page on the tank;''
 
* ''other literature.''
 
* ''other literature.''
  
 
{{France light tanks}}
 
{{France light tanks}}

Revision as of 17:08, 29 March 2019

RANK 5 FRANCE
Somua SM PACK
R.35 (SA38)
fr_renault_r39.png
R.35 (SA38)
AB RB SB
1.0 1.0 1.0
Class:
Research:2 900 Specs-Card-Exp.png
Purchase:700 Specs-Card-Lion.png
Show in game

Description

GarageImage R.35 (SA38).jpg


The Char léger d'accompagnement 1935 R (SA38) (Light support tank 1939 R) is a Rank I French light tank with a battle rating of 1.0 (AB/RB/SB). It was introduced in Update 1.75 "La Résistance". Although it is a "light tank", the R.39 feels pretty cumbersome in every way: slow reload speed, low max speed and bad acceleration. It actually feels more like an heavy tank...without the benefits of heavy armour. This tank's design is very reminiscent of other rank 1 French tanks, hence, players should be used to a subpar gun, "heavy" armour and low mobility.

General info

Survivability and armour

With good armour thickness and surprising hull angles, this tank can take some beating at a distance, provided you do not get a lucky shot in the turret ring or that you face a heavy-hitting gun. This should get you into effective combat ranges (500 - m) in relative safety. The most obvious weakspot is its turret flat left side, which is only 45 mm thick and badly angled, this makes hull-down position ineffective.

With its heavy side armour, one should use angles at its advantages and angle it at about 35° while facing opponents. Such an angling gives about 60 mm of effective thickness for 80% of the exposed area.

In an ambush position, this tank could face its opponents backwards (engine deck first). This unusual tactic could confuse enemies for a moment and provide extra protection as your engine may absorb shots. This will also decrease the chances of a lucky penetration : if turret is facing enemy, almost 90% of exposed surfaces have ~60 + mm of LoS thickness. If danger gets too high, you could give it the gas and "fly" away in forward motion.

Armour type:

  • Cast homogeneous armour
Armour Front (Slope angle) Sides Rear Roof
Hull 32 mm (13-64°) Front plate
22 mm (73-74°), 32 mm (24-26°) Front glacis
32 mm (0-74°) Lower glacis
32 mm (23°) Driver’s plate
40 mm (1-33°)
40 mm (1-2°)
40 mm (24-30°) Top
40 mm (9-32°) Bottom
25 mm
5 mm Engine grille
Turret 45 + 25 mm (5°) Turret front
45 mm (28-30°) Left side
25 mm (10-19°) Gun mantlet
40 mm (1-27°) 40 mm (8-63°) 25 mm
Armour Sides Roof
Cupola 40 mm 40 mm

Notes:

  • Suspension wheels, bogies, and tracks are all 15 mm thick.

Mobility

The mobility is this tank's biggest weakness: while it does not like long-range engagements and needs to close-up with its foes in order to damage them, its very low speed will always leave it far behind its allies. With its narrow tracks and poor power ratio (8.09 HP/ton), the R.39 hates being taken out in the mud as its speeds fall drastically. 20 km/h forward and -3 km/h backwards is all you'll get from this struggling 73 HP engine. Plan your moves in advance and do not stay too near to the front line as a successful retreat is hard to achieve with such a slow tank.

Mobility characteristic
Weight (tons) Add-on Armor
weight (tons)
Max speed (km/h)
11.0 N/A 22.2 (AB)
20.0 (RB/SB)
Engine power (horsepower)
Mode Stock Upgraded
Arcade 89 ___
Realistic/Simulator 73 ___
Power-to-weight ratio (hp/ton)
Mode Stock Upgraded
Arcade 8.09 __.__
Realistic/Simulator 6.64 _.__

Armaments

Main armament

Main article: SA38 L/33 (37 mm)

The 37 mm is not the best gun, but it can actually do some damage at reasonable ranges. Bear in mind its long reload time (for the BR) and back up into cover between shots. One should be an experimented tanker in order to use the most out of this gun as its post-penetration damage is poor: snipe crew members and modules one at a time. Avoid being too close to the front line as your slow reload speed makes multi-target engagement difficult. Your turret slewing rate is also an issue since you'll not be able to react in time to flanking opponents.

37 mm SA38 L/33
Capacity Vertical
guidance
Horizontal
guidance
Stabilizer
58 -8°/+12° ±180° Vertical
Turret rotation speed (°/s)
Mode Stock Upgraded Prior + Full crew Prior + Expert qualif. Prior + Ace qualif.
Arcade 9.30 _.__ _.__ _.__ _.__
Realistic 9.30 _.__ _.__ _.__ _.__
Reloading rate (seconds)
Stock Prior + Full crew Prior + Expert qualif. Prior + Ace qualif.
7.8 _.__ _.__ _.__
Ammunition
Penetration statistics
Ammunition Type of
warhead
Penetration in mm @ 0° Angle of Attack
10m 100m 500m 1000m 1500m 2000m
Mle1938 APC 47 44 37 28 20 17
Shell details
Ammunition Type of
warhead
Velocity
in m/s
Projectile
Mass in kg
Fuse delay

in m:

Fuse sensitivity

in mm:

Explosive Mass in g
(TNT equivalent):
Normalization At 30°
from horizontal:
Ricochet:
0% 50% 100%
Mle1938 APC 705 0.7 N/A N/A N/A ° 48° 63° 71°
Ammo racks
Ammo racks of the R.35 (SA38).
Full
ammo
1st
rack empty
2nd
rack empty
Visual
discrepancy
58 45 (+13) (+57) Yes

Machine guns

Main article: MAC 31 (7.5 mm)
7.5 mm MAC 31
Coaxial mount
Capacity (Belt capacity) Fire rate
(shots/minute)
Vertical
guidance
Horizontal
guidance
1,800 (150) 1,350 N/A N/A

Usage in battles

As with any French rank 1 vehicle, follow your allies and effectively be a support tank. With your low max speed, your role is very limited in the battlefield and resumes as such: stick to the frontline and try to avoid being shot at.

Support:

This is the intended role for this tank. As described in the "Vehicle characteristics" section, the R.39 should be held close to the frontline and provide covering fire for its allies. As this tank is slow, it means that it should never lead an assault. Go in with your allies and fall back with them.

Ambusher:

If your team gets destroyed and/or they flee their position, there you should not run with them as you will always be left behind by your faster allies. Instead, find yourself a narrow spot and wait for the enemy to go by. Shoot at them only if necessary as this tank performs poorly in multi-targets engagements. Use the "rearwards angling" tactics described in the "Armour" section earlier.

Pros and cons

Pros:

  • Tiny profile = tiny tank
  • Has one of the best French gun at rank 1
  • Has decent sloped hull armour
  • Has a very thick gun mantlet area: 10mm gun shield + 45 mm armour + 20 mm internal shield.
  • Thick sides allows for heavy angling

Cons:

  • Only one choice of ammunition, that one choice also has no explosive filler
  • Only two crew members, one knocked out means tank destroyed.
  • Extremely low speed, with bad cross-country and hill-climbing ability
  • Thin turret ring
  • Slow reload speed
  • Only 2 crew members in a cramped position (easy to one-shot)
  • Awful reverse speed of -3 km/h

History

Describe the history of the creation and combat usage of the ground vehicle in more detail than in the introduction. If the historical reference turns out to be too big, take it to a separate article, taking a link to the article about the vehicle and adding a block "/ History" (example: https://wiki.warthunder.com/(Vehicle-name)/History) and add a link to it here using the main template. Be sure to reference text and sources by using <ref>, as well as adding them at the end of the article. This section may also include the vehicle's dev blog entry (if applicable) and the in-game encyclopedia description (under === Encyclopedia Info ===, also if applicable).

Media

Excellent additions to the article would be video guides, screenshots from the game, and photos.

See also

Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:

  • reference to the series of the vehicles;
  • links to approximate analogues of other nations and research trees.

External links

Paste links to sources and external resources, such as:

  • topic on the official game forum;
  • encyclopedia page on the tank;
  • other literature.


France light tanks
AMC.34/35  AMC.34 YR · AMC.35 (ACG.1)
H.35/39  H.35 · H.39 · H.39 "Cambronne"
AMX-13  AMX-13 (FL11) · AMX-13-M24 · AMX-13 · AMX-13 (SS.11) · AMX-13-90 · AMX-13 (HOT)
Wheeled  AML-90 · AMX-10RC · Vextra 105
AMD.35  AMD.35 · AMD.35 (SA35)
E.B.R.  E.B.R. (1951) · E.B.R. (1954) · E.B.R. (1963)
Other  FCM.36 · R.35 (SA38) · Char 25t · MARS 15 · VBCI-2 (MCT30)
Austria  SK-105A2
Great Britain  ▄Crusader Mk.II
Netherlands  CV 9035NL
USA  LVT-4/40 · ▄M3A3 Stuart