You can identify by the sound when calling. The identifying number differ by the IP-Phone device you are using. Please refer to the following.

[Please refer to the original URL regarding the following table]

IP-phone device by NEC Platforms
*Formerly known as NEC Access Technica

The sound made when calling	Caller	Receiver
Do, Mi, So *Key of C, E, G.	IP	IP-Phone-C (and IP-Phone service provided by partner ISP)
Do, Mi *Key of C, E.		IP-Phone-C (and IP-Phone service provided by partner ISP) *The receiver is using NTT's IP-Phone-supported device
		Ordinary phone
		Mobile phone
		PHS
		International phone
No sound	PSTN (Public Switched Telephone Network)	IP-Phone service provided by different VoIP platform*1
		List of unsupported numbers Asahi Net IP-Phone-C: Numbers Outside the Scope of this Service
		"0000" + receiver's phone number

*1 Different VoIP platform refers to VoIP platform which cannot interactively connect with NTT Communications' VoIP platform.

NTT's IP-Phone-supported devices

The sound made when calling	Caller	Receiver
Toot toot toot toot *Four short toot sound.	IP	IP-Phone-C (and IP-Phone service provided by partner ISP)
		Ordinary phone
		Mobile phone
		PHS
		International phone
Toot toot toot toot, toot *Four short toot sound, continued by one long toot sound.	PSTN (Public Switched Telephone Network)	IP-Phone service provided by different VoIP platform*2
Toot toot toot toot, toot *Four short toot sound, continued by one long toot sound.PSTN (Public Switched Telephone Network)IP-Phone service provided by different VoIP platform*2		List of unsupported numbers Asahi Net IP-Phone-C: Numbers Outside the Scope of this Service
		3-digit phone number in the format 1XY (e.g., 110, 117) *184 and 186 are excluded.
No sound		"0000" + receiver's phone number
		Number starting with #

*2 Different VoIP platform refers to VoIP platform which cannot interactively connect with NTT Communications' VoIP platform.

The identification sound for NTT's supported IP-Phone may be different depending on the version of the firmware of your device.
Please contact NTT East/West for detailed firmware information.

Identification sound made when error happens

Status	Sound
Cannot connect even by redialing	Pip-pip, pip-pip, pip-pip... *Continuous pip sound.
Cannot connect temporariry	Toot, toot, toot... *Continuous toot sound.

Fujitsu FlashWave 2040 V1/Telephony Adapter IV-110SN by NEC
It differs depending on the version of firmware. Please refer to the following webpage to check for firmware version.

• Fujitsu FlashWave 2040 V1(Japanese)
• Telephony adapter by NEC: IV-110SN(Japanese)

Firmware version [up to R4.14.B37, 1.00-B26]

For Fujitsu FlashWave 2040 V1, the version should be up to R4.14.B37; for telephony adapter, the version of NEC IV-110SN should be up to 1.00-B26.

The sound made when calling	Caller	Receiver
No sound	IP	IP-Phone-C (and IP-Phone service provided by partner ISP)
	PSTN (Public Switched Telephone Network)	"0000" + receiver's phone number
Toot *One short toot sound.	IP	Ordinary phone
		International phone
Pip pip *Two short pip sound.		Mobile phone
		PHS
	PSTN	PSTN
Toot toot *Two short toot sound.	PSTN	Unsupported number

Firmware version [R4.14.B42 and above, 1.00-C12 and above]
For Fujitsu FlashWave 2040 V1, firmware version should be R4.14.B42 and above; for telephony adapter, the version of NEC IV-110SN should be 1.00-C12 and above.

Identification sound when calling: Caller | Receiver

The sound made when calling	Caller	Receiver
Do, Mi, So *Key of C, E, G.	IP	IP-Phone-C (and IP-Phone service provided by partner ISP)
Do, Mi *Key of C, E.		IP-Phone-C (and IP-Phone service provided by partner ISP) *The receiver is using NTT's IP-Phone-supported device
		Ordinary phone
		Mobile phone
		PHS
		International phone
No sound	PSTN (Public Switched Telephone Network)	Unsupported number
		"0000" + receiver's phone number

Identification sound made when error happens

Notes	Error (Firmware verseion: up to R4.14.B37)	Error (Firmware version: R4.14.B42 and above)
When you cannot connect with IP-Phone server (E.g., wrong IP-Phone device setting)	Pip pip pip, pip pip pip pip *Three short pip sounds, continued by four short pip sound.	Pip pip *Two short pip sound.