I can't pair BT headphones with iphone4

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iOS: Third-party Bluetooth headsets, headphones, and keyboards

How to pair with a Bluetooth accessory

1. Follow the instructions that came with the headset or car kit to make it discoverable or to set it to search for other Bluetooth accessories. This may involve entering a passkey or PIN (Personal Identification Number).
2. From the Home screen, choose Settings > Bluetooth, the iOS device searches for nearby Bluetooth accessories.
   Note: While your iOS device can maintain multiple pairing records, it can only connect to one headset or hands-free device at a time. This prevents your iOS device from sending your data to the wrong Bluetooth accessory.
3. Choose the Bluetooth accessory, and then enter a passkey or PIN if prompted.
   • Bluetooth headset: Refer to the documentation for the headset to determine the passkey.
   • Bluetooth keyboard: Type the passcode displayed on the iOS device on the Bluetooth keyboard and then press Return.
4. When pairing is complete, you can use the Bluetooth accessory with your iOS device.

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Unable to pair with Bluetooth accessory

1. Ensure that the Bluetooth accessory is in range. Most devices have a range of approximately 30 feet.
2. If a pairing record already exists with the Bluetooth accessory, the device will not show up as discoverable. Try connecting the device using that pairing record, or delete the record and try to pair again.
3. Ensure that the firmware or software on the Bluetooth accessory is up to date.
4. Verify the PIN for the device. You may need to refer to your manufacturer's documentation for this.
5. Ensure that the Bluetooth accessory is charged or connected to power.
6. Turn off both the iOS device and the Bluetooth accessory, then turn both devices on again.
7. If the issue persists, test Bluetooth with another device or consult the manufacturer's documentation.

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Are the headphones made to work with iPhone4?

Are they still paired to another device?

Did you try to reset the phone by holding the sleep and home button for about 10sec, until the Apple logo comes back again? You will not lose data by resetting, but it can cure some glitches.