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UAFX Astra Modulation Machine Manual

This article contains complete operating instructions for the UAFX Astra Modulation Machine effects pedal. 

 


A Letter From Bill Putnam, Jr.

Congratulations on your new UAFX pedal. We know that buying any new piece of gear requires an investment of time and money, and we aim to make your investment pay off!

At UA, we are dedicated to the idea of building “instant classics” — the type of music and audio gear that delivers album-worthy sounds to inspire you for decades.

UAFX pedals represent more than 20 years of research into vintage analog effects, coupled with next-generation digital engineering and rock-solid reliability.

Please let us know how we’re doing. Feel free to reach out to us via our website www.uaudio.com, and via our social media channels.

Thank you for your support, and enjoy your sonic exploration!

Sincerely,

Bill Putnam Jr.

 


Astra Quick Start


Astra Power

Note: Power supply sold separately.

UAFX pedals require an isolated 9 volt DC, center negative, 2.1 x 5.5 mm barrel connector (same as standard Boss connectors) power supply, which can provide 400 mA (milliamps) of current. Each UAFX pedal must be connected to a separate power supply, or connected to an isolated power connection from a multi-output power supply. Connect the power supply to the 9VDC connector on the pedal’s rear panel. 

When you first connect your UAFX pedal to a power supply, the Effect LEDs cycle, showing that the pedal is starting up. The startup sequence takes about 15 seconds. Your dry audio signal passes through the pedal during startup.

If power to your UAFX pedal is interrupted during operation, processed audio stops. However, your dry audio signal still passes through the pedal. When the pedal is unpowered, and when it’s starting up, the signals are pure analog dry-through from input to output, without buffering or any other circuitry, via mechanical relays. 

Important Power Notes 

  • Each UAFX pedal requires 400 mA of current. Make sure your power supply can deliver at least 400 mA to the pedal for proper operation and performance.

  • An isolated supply provides power and grounding that is electrically separated, usually by means of a transformer for each connector. Some low-cost power supplies might have separate connectors, but might not provide true ground and power isolation, causing noise and ground loop hum. 

  • If your power supply has multiple outputs, make sure that each output provides true isolation, or that you connect your pedal to its own power supply.

  • It’s OK to connect a power supply that can deliver more than 400 mA. The pedal only draws the current it needs and will not be damaged if the supply is 9VDC.

  • If your power supply is not isolated, you might hear additional hum in the pedal signals. If the supply cannot provide 400 mA of current, the pedal might not operate properly, even if the LEDs and switches seem to be working. 

  • Daisy-chaining (running multiple pedals from one output of a power supply) is not supported.

 


Astra Connections

All UAFX audio jacks accept 1/4" (6.35 mm) unbalanced TS (Tip-Sleeve) instrument cables. Although TRS (Tip-Ring-Sleeve) cables may be used, they offer no benefit over TS cables.

Your UAFX pedal senses which jacks are connected and adjusts the internal signal routing automatically. Stereo inputs are processed in true stereo, and output as either stereo or mono depending on the connected outputs.

Important: You must connect to UAFX’s IN 1/MONO jack. The IN 2/STEREO jack doesn’t work by itself without the IN 1/MONO connection. 

UAFX pedals are designed with enough headroom to easily accommodate instrument levels and amp effects loop levels, but they can also handle line-level gear such as synthesizers and audio interfaces. The pedals are voiced for instrument levels, so you may need to reduce the line out level of the gear you’re connecting into the pedals to avoid overdriving the effects.

The USB-C port is for pedal registration and firmware updates only, within the UAFX Control desktop app for Mac and Windows computers. You can connect to any type of USB port on the computer, but you may need an adapter.

The PAIR button and LED are for pedal registration and global pedal settings (bypass and footswitch modes) only, via the UAFX Control mobile app.

 

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Connection Examples

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Mono in > Mono Out

 

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Mono in > Stereo out

 

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Stereo in > stereo out

 

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Pedal in amp’s effects loop

 

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Pedal in dual amp stereo setup showing effects loop connections for both amps

 


Astra Overview

The Pinnacle of Classic Chorus, Flanging/Doubling, and Tube Tremolo Effects 

Taking you deep down the rabbit hole of classic analog modulation, UAFX Astra Modulation Machine serves up the most sonically authentic bucket-brigade chorus/vibrato, studio flanger/doubler, and tube-driven tremolo effects ever placed into a single stompbox.

Built upon our powerful new UAFX dual-engine processing and unmatched levels of quirky analog realism, Astra delivers richly addictive vintage modulation, beautifully crafted to inspire you for decades.

Dual Stereo Modulation Engines for Endless Creativity 

Astra's UAFX engine powers separate stereo instances of each modulation effect, thanks to its unique dual-engine processing. It's like having two bucket-brigade hardware units running simultaneously — or even dual tremolo circuits — giving you a full stereo spread of complex, jaw-dropping textures. 

Silent Switching

UAFX pedals are designed to switch on and off seamlessly and silently, using relays and advanced circuitry.  When in true bypass, you may hear the mechanical relay switching from the hardware, but you do not hear the switching in the audio signal. There are no mechanical noises from the pedal with buffered bypass because the physical relay is not used. 

 

Free Bonus Effects

To get the free Phaser X90 and Dharma Trem 61 modulation effects, register your pedal with UAFX Control software. To get UAFX Control, visit:

 


Astra Operation

Live Mode and Preset Mode

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In Live mode, the sound reflects the current positions of the knobs, switches, and LEDs on the pedal, and the left footswitch toggles the Live mode effect on/off.

In Preset mode, you hear the settings that are stored as a preset, and the current positions of the knobs and switches do not reflect the sound. Instead, all knob and switch positions are internally set to their stored positions, and the right footswitch toggles the preset effect on/off.

Live Mode

To enter Live mode, press the left footswitch. Press the left footswitch again to toggle the live effect on/off. The left footswitch LED is lit red when the Live mode effect is on.

Preset Mode

To enter Preset mode, press the right footswitch. Press the right footswitch again to toggle the preset on/off. The right footswitch LED is lit green when the preset is on.

golden-switches-preset-led.png

Note: The right footswitch (see below) can be set to other behaviors in the UAFX Control mobile app.

 

Right Footswitch

The behaviors of the right footswitch can be changed to suit your preferences with the UAFX Control mobile app. Note that the left footswitch always toggles Live mode, where the knobs and switches are “what you see is what you hear” (except the speed knob, if tempo is tapped).

Astra’s right footswitch has two available settings:

Preset*

Live mode and Preset mode are available. Tap tempo is unavailable.

Preset + Tap

Live mode, Preset mode, and Tap Tempo for both modes are available.

*Default setting from factory and after restoring defaults

Preset

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When set to Preset, the right footswitch immediately loads the preset with its stored tempo, and toggles the preset on/off. Tap tempo is unavailable with this setting.

Preset + Tap

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When set to Preset + Tap, the right footswitch performs multiple functions.

Load Preset: Hold the right footswitch for 1.5 seconds (or longer) to load the preset with its stored tempo when the footswitch is released. The Effect Type LED blinks rapidly when the preset is armed for loading. 

Bypass Preset: Hold the right footswitch for 1.5 seconds (or longer) to bypass the preset when the footswitch is released. The Effect Type LED blinks rapidly when the preset is armed for bypass. Tip: Tap the left footswitch twice to quickly bypass the pedal from Preset mode.

Tap Live/Preset Tempos: Short-press (don’t hold) the right footswitch twice or more to tap quarter note tempo. In Live mode, the right footswitch LED blinks red at the current tempo. In Preset mode, the right footswitch LED blinks green at the current tempo.

 

Stored Preset

You can store a preset on your UAFX pedal, and recall it using the right footswitch. A default factory preset is included.

When you store a preset while in Live mode, the position of all knobs and switches on the pedal are saved. So when you make a great sound in Live mode, storing it is as easy as holding down the store switch. 

When you store a preset while in Preset mode, only those knobs and switches that have changed since you loaded the preset are saved. So, when saving in Preset mode, what you hear is what is saved, and not the current positions of the knobs and switches. 

To store your sound as a preset

  1. Set your sound as you want it stored in the preset. 

  2. Press and hold the STORE switch in the down position until the green PRESET footswitch LED blinks rapidly (about 0.5 seconds).

Preset Notes

  • The speed in Preset mode and Live mode are completely independent.

  • When you move a knob or switch in Preset mode, the settings for the sound immediately jump to the new knob or switch position. 

  • When you switch the effect type in Preset mode, all settings change to their defaults, which are optimized for that effect. Use the defaults as a starting point when you are looking for a great chorus, flanger, or tremolo sound.

 

Effect Bypass Routing

Astra Modulation Machine effect bypass routing can be set for true bypass or buffered bypass using the UAFX Control mobile app. Bypass routing determines how the pedal behaves when the effect is off.

 

True Bypass

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When bypass routing is set for true bypass and the effect is off, the dry signal is pure analog dry-through from input to output, without buffering or any other circuitry, via mechanical relays. By default, your UAFX pedal is set for true bypass. 

When set for true bypass and the effect is on, the output is buffered.

Buffered Bypass

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Buffered bypass can be set in the UAFX Control mobile app. When bypass routing is set for buffered bypass, the output is buffered when the effect is on, and also when the effect is off. 

When the effect is off, the dry signal remains analog dry-through.

 

 


Astra Controls

Astra Modulation Machine’s knobs and switches control each modulation effect similarly, but the functions of the controls vary, depending on the currently selected effect. See the individual modulation effect details section for complete control descriptions.

Speed

Adjusts the modulation rate.

Depth

Adjusts the modulation amount.

Intensity

Adjusts aspects of the modulation character, depending on the effect.

Shade

Adjusts aspects of the modulation character, depending on the effect.

Shape

Adjusts aspects of the modulation character, depending on the effect.

Effect Type

Push this switch up or down to change the modulation model. When you push the switch repeatedly, the pedal cycles through all available effects. 

Tip: Register your pedal to get the bonus Phaser X90 and Dharma Trem 61 effects.

Effect Type LED

The currently selected effect is indicated by this LED. A red LED indicates that the effect printed on the pedal is selected. The bonus Phaser X90 effect is selected when the top LED is green, and the bonus Dharma Trem 61 effect is selected when the middle LED is green (the bonus effects don’t have labels).

Store

The STORE switch saves the current sound as a preset. Press and hold the STORE switch in the down position until the green PRESET footswitch LED blinks rapidly (about 0.5 seconds).

See the Stored Preset section for additional details.

Variation A/B

Each modulation model (Chorus Brigade, Flager Dblr, Trem 65, Phaser X90, Dharma Trem 61) includes two variations that are selectable with the A/B switch. These modes are unique variations within each modulation type. 

Use the A/B switch to select variations within the selected modulation type. The variations for each effect are shown in the effect details section

Left Footswitch LED

The left footswitch LED is lit red when the live knob and switch settings are active. 

Left Footswitch

Press to toggle the effect on/off with current knob and switch settings.

Right Footswitch LED

By default, the right footswitch LED  is lit green when the preset is on. Other behaviors are possible, depending on the right footswitch setting. 

Right PRESET Footswitch

The right footswitch can be set to access the preset, or provide tap tempo and access to the preset. See Right Footswitch for more information 

 


Astra Effect Details

Each UAFX effect has a unique sound and control set. The specific function of the knobs and switches within each effect varies, depending on which functions are needed for optimal control of the specific effect. 

This section contains the specific control details for each effect, along with a controls map diagram for quick reference. You can download the control map diagrams, along with a blank recall sheet for noting your own settings, via the link below.

Chorus Brigade

Iconic Japanese Modulation

Upon its release in 1976, this legendary gray bucket-brigade stompbox changed the sound of music with its thick, luxuriant chorus and wavy vibrato. Astra's Brigade Chorus mode gives you the most complete circuit emulation of this landmark unit — including its preamp section for authentically thick, saturated sounds — letting you paint with subtle ripples of analog texture and tone, adding chewiness, shimmer, and motion to everything you play.

Note: With Chorus Brigade, some knobs do not function. To reproduce the original sonics as accurately as possible, the control set from the original hardware is provided. When you turn a knob that is inactive, the Effect Type LED blinks rapidly, indicating that the knob has no function. 

Control Details (Chorus)

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Control

Description

Additional Info

Speed

No function (N/A)

When turning, the Effect Type LED blinks to indicate knob is inactive

Depth

No function (N/A)

When turning, the Effect Type LED blinks to indicate knob is inactive

Intensity

Chorus intensity

Combines speed and depth on a single control 

Shade

Output level

Noon is unity gain

Shape

No function (N/A)

When turning, the Effect Type LED blinks to indicate knob is inactive

Mode 

When used in stereo, sets mode to classic or dual stereo

In classic mode, dry signal appears at left output, and wet signal appears at the right output. 

In dual stereo mode, the pedal processes each side separately, with the left and right chorus LFOs 90º out of phase for maximum effect.

 

Control Details (Vibrato)

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Control

Description

Additional Info

Speed

Vibrato rate

 

Depth

Vibrato depth

 

Intensity

No function (N/A)

When turning, the Effect Type LED blinks to indicate knob is inactive.

Shade

Output level

Noon is unity gain.

Shape

No function (N/A)

When turning, the Effect Type LED blinks to indicate knob is inactive.

Mode 

When used in stereo, sets the mode to classic or dual stereo.

In classic mode, dry signal appears at left output, and wet signal appears at the right output. 

In dual stereo mode, the pedal processes each side separately, with the left and right vibrato LFOs 90º out of phase for maximum effect.

 

Flanger Dblr

A Rackmount Studio Classic

Packed with late-'70s bucket-brigade tech, this classic rackmount studio flanger/doubler is famous for stunning whoosh effects, organic thickening, and a parade of wild sounds that go way beyond typical flanger boxes. Astra's Flanger/Dblr effect is the only end-to-end circuit emulation of this ultra-rare unit, capturing its original features to a "T" and putting impossibly dense, complex flanging/doubling right at your feet.

Note: With Flanger Dblr, when the Right Footswitch is set to Preset + Tap, the tempo is set to 1/8th notes, and controls the flanger/doubler rate. 

Control Details

astra-map-flanger-dblr.png

Control

Description

Additional Info

Speed

Rate

The rate of modulation applied to the delay time LFO.

Depth

Width

The amount of modulation applied to the delay time LFO.

Intensity

Regeneration (feedback) amount

The amount of effect routed back to its input; as the value increases, a more resonant signal is produced.

Shade

Wet/dry mix

Noon is max flange (50% wet).

Shape

Manual sweep

The delay time; adjusts the overall sound, imparting different vowel-like qualities in the sweep.

Mode

Normal or inverted

Inverts the phase for a more hollow sound.

Variation A

Flanger mode

Use for a classic flanging sound.

Variation B

Doubler mode

At short settings, this creates more of a doubling effect, at longer settings creates more of a chorus-like sound.

 

Trem 65

Authentic Tube Amp "Shake"

Few things compare to the optical tube-driven tremolo of '60s American amplifiers. Deep, undulating, and the very essence of vibe, Trem 65 is a faithful emulation of this classic circuit. From shimmering ripples to choppy mayhem, every dynamic detail is captured in UA style, down to the complex interactions between the light source photoresistor and 12AT7 driver tube. Plus, you can explore further and create your own trem textures with variable sine and square wave settings.

Control Details

astra-map-trem-65.png

Control

Description

Additional Info

Speed

Rate

Slower speeds have more depth, mimicking the behavior of the optical tube circuit.

Depth

Intensity

Like original tube circuit, at higher speeds the Intensity has less effect

Intensity

LFO Shape

Adds subtle edges to the waveform

Shade

Input drive

Noon is unity gain. Increase this control to compensate for the perceived volumes drops in volume that can occur with tremolo. 

Shape

No function (N/A)

When turning, the Effect Type LED blinks to indicate the knob is inactive.

Mode

Dual mono or stereo panned

When stereo panned, tremolo pans 180º left and right on each swing.

Variation A

Sine wave

Sounds like the original tube circuit.

Variation B

Square wave

The sine wave is squared off for a more aggressive sound.

 

Phaser X90

Classic Phasing Effects

Based on the classic “script” and “block” phaser effects — available as a free bonus with pedal registration. 

Register to get this effect

This additional effect is available after you register your Astra Modulation Machine. To select the Phaser X90 effect, push the Effect Type switch to cycle through the modulation effects. Phaser X90 is selected when the top Effect Type LED is lit green (the bonus effects don’t have labels).

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Control Details

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Control

Description

Additional Info

Speed

Rate

Speed range is different between Script and Block circuits.

Depth

No function (N/A)

When turning, the Effect Type LED blinks to indicate the knob is inactive.

Intensity

No function (N/A)

When turning, the Effect Type LED blinks to indicate the knob is inactive.

Shade

Input drive

Noon is the stock setting, turn up for more harmonics.

Shape

No function (N/A)

When turning, the Effect Type LED blinks to indicate the knob is inactive.

Mode 

LFO Mono/Stereo Phase

In Stereo Phase, the two sides are 180º out of phase, for a swirling, three-dimensional sound,

Variation A

Script circuit

Smooth and slow phase, for classic hard rock tones.

Variation B

Block circuit

Faster, more “chewy” phase, with higher max speed and feedback in the phase circuit. 

 

Dharma Trem 61

Unique Dynamically Controlled Harmonic Tremolo

Harmonic tremolo is a unique combination of tremolo and phasing, where the signal is split into bass and treble components that are then panned between the filters with an LFO. These split signals are then summed back into a single signal, with the result being a tremolo that has both volume and phase-like components. 

With Dharma Trem 61, you can control the crossover frequency of the bass and treble components, and add dynamic control of the tremolo speed. The end result is a “dynamic harmonic tremolo,” a unique effect unlike anything else available. Dharma Trem 61 is available as a free bonus with pedal registration.

Register to get this effect

This additional effect is available after you register your Astra Modulation Machine. To select the Dharma Trem 61 effect, push the Effect Type switch to cycle through the modulation effects. Dharma Trem 61 is selected when the middle Effect Type LED is lit green (the bonus effects don’t have labels).

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Control Details

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Control

Description

Additional Info

Speed

Rate

Baseline speed, which can be modified by dynamic controls.

Depth

Depth

Interactive with Intensity; depth is consistent at any speed.

Intensity

Crossover from tremolo to pitch phase

Set at 10 o’clock for univibe-like sound, and set this fully on or off for authentic harmonic tremolo only with no pitch warble.

Shade

Dynamic speed threshold

Sets the threshold at which the dynamic speed is triggered. Start at noon and adjust to taste.

Shape

Dynamic speed amount

 

Turn Shape all the way down to disable dynamic control for classic early ‘60’s harmonic tremolo.

 

Sets the dynamic speed; when the Dynamic speed threshold is exceeded, the rate ramps up or down to this speed, then ramps back to the speed set on the Speed knob or via tap tempo. 

Mode 

Dual mono/LFO stereo phase

When set to LFO stereo phase, tremolo swings 180° left and right.

Variation A

Classic

Traditional harmonic tremolo

Variation B

Vibey

Phaser-like harmonic tremolo

 

Astra Default Preset

The default preset for Astra Modulation Machine provides a classic amp tremolo sound. You can replace this preset by storing your own.

Note that when you switch effect types in Preset mode, all settings change to their defaults, which are optimized for that effect. Use the defaults as a starting point when you are looking for a great chorus, flanger, or tremolo sound.

uafx-default-astra.png

 


Astra Specifications

All specifications are subject to change without notice.

Power requirements
(power supply sold separately)

Isolated 9VDC, center-negative, 400mA minimum 

Inputs

2 x ¼” unbalanced TS
(input 2 for stereo connections)

Outputs

2 x ¼” unbalanced TS
(output 2 for stereo connections)

Bypass modes
(switchable within UAFX Control mobile app)

True bypass via mechanical relays or buffered bypass

Input impedance

500 Kilohms (Mono In)
1 Megohms (Stereo In)

Output impedance

500 Ohms

Maximum input level

12.2 dBu

Maximum output level

12.1 dBu

Frequency response

20 Hz to 20 kHz, ±3 dB

USB Type-C

For registration and firmware updates via computer

Wireless technology

Bluetooth v5

Dimensions
(with knobs and protrusions)

Height: 2.56 inches, 6.5 cm
Width: 3.62 inches, 9.2 cm
Depth: 5.55 inches, 14.1 cm

Weight (unboxed)

1.24 lbs
0.567 kg

 

 

 


Astra Safety

safety-symbol-exclaim.pngCaution: To help maintain the safety of your product, the chosen power supply must be a certified power supply complying with Limited Power Source (LPS) requirements with the following characteristics and electrical ratings: Isolated 9VDC, center-negative, 400 mA minimum, 2.1x5.5 mm barrel connector. Additional details at help.uaudio.com.

safety-symbol-book-info.pngBefore using this unit, be sure to carefully read the applicable items of these operating instructions and the safety suggestions. Afterwards, keep them handy for future reference. Take special care to follow the warnings indicated on the unit, as well as in the operating instructions.

  • Read the instructions.

  • Keep these instructions.

  • Heed all warnings.

  • Follow all instructions.

  • Do not use this apparatus near water.

  • Clean only with dry cloth.

  • Do not block any ventilation openings. Install in accordance with the manufacturer’s instructions.

  • Do not install near any heat source such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.

  • Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other.

  • Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles, and the point where they exit from the apparatus.

  • Only use with attachments/accessories specified by the manufacturer.

  • Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been dropped.

  • Astra Modulation Machine does not contain a fuse or any other user-replaceable parts.

  • A compliance marking label is provided on bottom of the unit. 

United States Class B Manual Statement

NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try and correct the interference by one or more of the following measures:

  • Reorient or relocate the receiving antenna. 

  • Increase the separation between the equipment and the receiver.

  • Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

  • Consult the dealer or an experienced radio/TV technician for help. 

Japanese Class B Manual Statement

この装置は、クラスB機器です。この装置は、住宅環境で使用することを目的としています  が、この装置がラジオやテレビジョン受信機に近接して使用されると、受信障害を引き起こ. すことがあります。取扱説明書に従って正しい取り扱いをして下さい。VCCI-B

This is Class B equipment. Although this equipment is intended for use in residential environment, it could cause poor reception if used near a radio television receiver. Please follow instructions in the instruction manual.

Korea KCC: 해당 무선설비는 전파혼신 가능성이 있으므로 인명안전과 관련된 서비스는 할 수 없습니다.

License exempt. This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and (2) this device must accept any interference, including interference that may cause undesired operation of the device.

Le présent appareil est conforme aux CNR d'Industrie Canada applicables aux appareils radio exempts de licence. L'exploitation est autorisée aux deux conditions suivantes : (1) l'appareil ne doit pas produire de brouillage, et (2) l'utilisateur de l'appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible d'en compromettre le  fonctionnement.

safety-symbol-trash.pngUsed electrical and electronic equipment should not be mixed with general household waste. Please dispose in accordance with local regulations.

  • IEC 62368-1

  • FCC ID: 2AXKQ2029

  • IC ID: 26610-2029

 

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