---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21206#article
headline: "21206: Invalid SendDigits"
url: https://www.twilio.com/docs/api/errors/21206
inLanguage: en
dateModified: 2026-03-11T18:38:39.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21206: Invalid SendDigits

Log Type: APPLICATION

Log Level: ERROR

## Description

You attempted to initiate an outbound phone call, and you included a `SendDigits` parameter that wasn't valid. `SendDigits` is optional, and specifies that Twilio should simulate sending keypad digits when the party answers. `SendDigits` may contain numbers, the `#` and `*` characters, the letters `A`, `B`, `C`, `D`, as well as lowercase `w` to "wait" for half a second or uppercase `W` to "wait" for a full second.

### Possible causes

The parameter `SendDigits` includes an invalid character.

### Possible solutions

Ensure the `SendDigits` parameter only contains the characters: `0123456789ABCD*#wW`.