How DTMF works on a call
Every key on a phone keypad sits in a row and a column, and each row and each column has its own tone. Pressing a key plays its row tone and column tone together. The system at the other end hears the pair and knows which key it was. That's how "press 1 to confirm" menus work on any phone, including basic feature phones.
When keypad input beats speech
Speech is easier for most questions. Keypad input is better when:
- The input is a long number, such as an order ID or a registered mobile number, that's easy to mishear on a noisy line.
- The caller is in public and would rather not say details out loud.
- The answer is a simple choice on a confirmation call.
Here's a cash-on-delivery confirmation:
- Agent: "Aapka ₹1,299 ka order kal deliver hoga. Confirm karne ke liye 1 dabaiye, ya bas 'haan' boliye."
- Caller: (presses 1)
- Agent: "Dhanyavaad, aapka order confirm ho gaya."
Why it matters
Offering both speech and keys gives every caller a way through: someone on a busy street, someone with a strong accent the agent struggles with, or someone who simply prefers pressing keys to talking to an AI.
How Kallix uses it
Kallix agents read keypad (DTMF) input, so callers can enter a number or pick an option mid-conversation. By design, Kallix agents never ask for card numbers, OTPs, PINs or passwords, by voice or by keypad. For payments, they send a payment link on WhatsApp instead.