Sazrika Foundation / Free tools / DTMF Test Line
Free tool

DTMF test line

Call our free test number to hear your caller ID read back, check your STIR/SHAKEN attestation level, and test your DTMF keypad tones. Works from anywhere in the world.

// Call this number

+1 540 305 3020

Free to call from most VoIP clients · Standard rates apply from PSTN

Call now
// What you'll hear
1
Your caller ID read back
The line announces your phone number exactly as received by the server — useful for verifying what number you're presenting.
"Your caller ID is: +6, 0, 1, 2, 3..."
2
STIR/SHAKEN attestation level
US callers hear their attestation level — A, B, or C. International callers skip this step as STIR/SHAKEN is US-only.
"Attestation level A — full attestation."
3
DTMF echo test
Press any key on your keypad. The line announces which key you pressed and plays the DTMF tone back so you can verify your keypad is sending correctly.
"You pressed five." [tone plays]
★
Press * to repeat menu · Press # to end
Stay on the line and keep testing as many keys as you need. Press # when done.
// Keypad reference
1
2
ABC
3
DEF
4
GHI
5
JKL
6
MNO
7
PQRS
8
TUV
9
WXYZ
*
Repeat menu
0
+
#
End call
// STIR/SHAKEN attestation levels (US only)
A
Full attestation
Your carrier fully verified you as a customer and confirmed you are authorised to use this number. Highest trust level — least likely to be flagged as spam.
B
Partial attestation
Your carrier knows who you are but cannot confirm you own this specific number. Common with hosted PBX or SIP trunking customers.
C
Gateway attestation
The call entered the US phone network through a gateway and the carrier has limited information. Common with international calls entering the US PSTN.
—
No attestation (international callers)
STIR/SHAKEN is a US standard. Callers from outside the US will not receive an attestation reading — this is expected and normal.

ⓘ Note: This is a US Twilio number. Standard international call rates apply when calling from outside the US. Most VoIP softphones and SIP clients can call this number for free. STIR/SHAKEN attestation data is only available for calls originating from US carriers.