Before your flight
- Charge Relay and test it with a laptop’s 3.5 mm output.
- Pair your headphones before boarding.
- Turn Relay off using the side switch after testing.
INTERACTIVE USER GUIDE · RELAY / TC218
Hear airplane audio in your own Bluetooth headphones.
Relay sends sound from a 3.5 mm audio output to AirPods or Bluetooth headphones. It is a transmitter—not a device you select on your phone.
Download full manual (PDF) ↗
Two headphones3.5 mm audioFirst, know what connects to what
Relay sits between the screen and your headphones.
Audio source3.5 mm AUDIO OUT
→RelayBluetooth transmitter
→HeadphonesAirPods / Bluetooth
Do not look for “Relay” in your iPhone Bluetooth menu. Pair the headphones directly with Relay.
QUICK SETUP
Four steps. One clear result.
Keep Relay and your headphones within 3 ft / 1 m while pairing.
STEP 1
Put your headphones in pairing mode.
Turn off Bluetooth on nearby phones and computers first.
Put AirPods in pairing mode
- AirPods 1–3 and AirPods Pro 1–2: keep them in the case, open the lid, then hold the button on the back for about 5 seconds.
- AirPods 4: keep them in the case, open the lid, then double-tap the front of the case.
- Ready when the case light flashes white.
✓
Success: the headphone or case light flashes rapidly.
STEP 2
Turn on Relay.
Slide the side power switch to ON.
Red + blue flashingRelay is ready to pair
Still only seeing a blue flash?
Press and hold the large round MFB for 2 seconds.
Do not continue until the light flashes red and blue.
STEP 3
Wait for a solid blue light.
Keep both devices close. Connection usually takes a few seconds.
Solid blueConnected—go to the next step
Know the difference
Red + blueStill pairing
Blue every 1 secTrying to reconnect
Blue every 5 secNot connected
STEP 4
Plug into AUDIO OUT and press play.
Use a 3.5 mm headphone/audio output on the airplane screen, laptop, or gym machine.
Important: check all 3 volumes
1SourceAirplane screen
→
2Relay+ / − buttons
→
3HeadphonesVolume control
If any one is muted or too low, you may hear little or no sound—even with a solid blue light.
- Make sure the plug is fully inserted.
- Press play on the audio source.
- Start low, then raise the source, Relay, and headphone volumes.
✓
Done: solid blue + sound in your headphones.
USE RELAY
Travel, reconnect, or share.
Reconnect
- Turn off phone Bluetooth.
- Turn on your headphones, then Relay.
- If needed, press MFB once to reconnect the last device.
Add a second headphone
- Keep headphone 1 connected—its Relay light must be solid blue.
- Hold Relay MFB for 2 seconds.
- Put headphone 2 in pairing mode.
- Both headphone lights on Relay should be solid blue.
ON THE PLANE
Choose the correct audio jack.
Relay needs an analog 3.5 mm headphone output.
Single 3.5 mm
Plug Relay in directly.
Dual 3.5 mm
Use the included airplane adapter.
Mixed-size jacks
Use only the 3.5 mm headphone jack.
QUICK FIXES
What do you see?
Choose the symptom—not a long troubleshooting list.
Only blue is flashingRelay is not in pairing mode
- Hold MFB for 2 seconds.
- Wait for alternating red + blue.
- If nothing changes, turn Relay off and on, then try again.
Red + blue, but no connectionHeadphones may not be ready
- Turn off Bluetooth on nearby phones, tablets, and computers.
- Confirm the headphone light is flashing rapidly.
- Keep both devices within 3 ft / 1 m and restart pairing.
Solid blue, but no soundConnected—check all 3 volume controls
- Use a 3.5 mm headphone or AUDIO OUT port.
- Fully reinsert the plug and press play.
- Raise all three: source / airplane screen → Relay (+ / −) → headphones.
②Only one headphone worksDual-link needs careful pairing
- Turn off Bluetooth on all nearby devices.
- Keep headphone 1 connected while pairing headphone 2.
- If headphone 2 has no sound, put both earbuds in their cases, restart Relay, then remove both sets.
- For best stability, use two over-ear headphones or two identical earbud sets.
↺Clear all saved pairingsFactory reset
- Turn Relay on.
- Hold + and − together for 6 seconds.
- The lights appear pink for 3 seconds, then flash red + blue alternately.
This clears every saved pairing. Avantree does not document a one-device erase command.
◷Audio is delayedSome Bluetooth delay is normal
- For lower delay, use headphones that support aptX Low Latency or aptX Adaptive.
- Keep devices close and away from crowded wireless areas.
- Relay is not recommended for instruments or real-time monitoring.
Will Relay turn itself off?Use the side switch to turn Relay OFF after use. Do not rely on an automatic shutoff.
REFERENCE
Buttons, lights, charging.
Buttons
- Power switch
- Slide ON / OFF
- + / −
- Press to adjust volume
- + and −
- Hold 6 sec to clear all pairing history
- MFB
- Hold 2 sec: pairing mode
- MFB
- Press once: reconnect last device
- MFB
- Double-click: check battery
Connection lights
- Red + blue
- Pairing
- Solid blue
- Connected
- Blue / 1 sec
- Reconnecting
- Blue / 5 sec
- Standby—not connected
- Pink / 3 sec
- Pairing history cleared
USB-C CHARGING
About 2 hours to charge.
- Use a 5 V USB power source rated 500 mA–2 A.
- Any battery LED flashing: charging.
- All battery LEDs off: fully charged.
- Up to 25 hours playtime; actual life varies with use.
PRODUCT DETAILS
What is included—and what Relay supports.
Compatibility
✓
Works withAirPods and Bluetooth headphones; airplane screens, laptops and gym machines with 3.5 mm AUDIO OUT.
×
Not designed forPairing to phones/tablets, TVs, hearing aids, musical instruments or real-time monitoring.
!
Signal generatorsOnly use an analog 3.5 mm headphone/audio output. Bluetooth delay makes Relay unsuitable for real-time work.
Specifications
BluetoothVersion 5.3
ProfilesA2DP, AVRCP
CodecsaptX Adaptive / LL / HD, aptX, SBC
RangeUp to 33 ft / 10 m
PlaytimeUp to 25 hours
ChargingAbout 2 hours
Size125 × 24 × 12 mm
Weight15 g
SAFETY
Listen safely. Travel responsibly.
Lower volume before putting on headphones, then increase it gradually. Stop if you experience ringing or discomfort.
Keep the product dry. Do not open it or replace the built-in battery. Keep small parts away from children.
Follow airline and facility instructions for wireless devices. Do not use headphones where full attention is required.
STILL NEED HELP?
Talk to a real support agent.
Include “Relay / TC218,” your headphone model, and the light pattern you see.