Voice API - Play Audio and Collect Digits

You can use the Voice API to play a message and collect digits from your end user. You can do this in an outbound call, or in response to an inbound call. This can be used to create simple phone trees, or collect information from your customer by associating each digit with a choice.



If you are interested in trying TeleSign's Voice API, sign up by contacting our experts.


You must have the following:

  • TeleSign credentials: Your Customer ID and API key
  • Customer event URL: A notification service you have set up for TeleSign to post event information to. For more details, refer to the Set up the Customer Event URL section on the Voice API Reference page.

If you do not want to use your own number, you should also have:

  • TeleSign phone number: A phone number you have purchased from TeleSign to use as a caller ID. Purchase a number using the TeleSign Phone Numbers API (see Get Started with the Phone Numbers API) or ask our Customer Support Team to purchase a number for you. Make sure that the number is voice-capable (include the parameter and value voice_capable=true in your request to the Phone Numbers API). Refer to Get Started with the Phone Numbers API for more details.



For further technical details, including definitions for each parameter, see Voice API Reference.



Use only codecs and standards for audio files supported by the Voice API. See Supported Standards and Codecs for more details.

Implement Stream Audio and Collect Digits

This section walks you through dialing a number, playing a message, and collecting digits from an end user. You could also begin this process by receiving an inbound call, then playing a message and collecting digits. If you want to start that way, see the Receive an Inbound Call page.

To set up the call, you do the following:

  1. You create an outbound call using the dial action. You add a destination phone number for to and your callerID (phone number you bought from TeleSign) goes in the caller_id_number field if you decide to use a caller ID (recommended). If you reviewed the Make an Outbound Call page, this will look familiar.

Outbound Call with Python

from base64 import b64encode

import requests

customer_id = 'Your Customer ID goes here.'
api_key = 'Your API key goes here.'

destination_number = 'The complete phone number you want to call, including country code, with no special characters or spaces.'
caller_id_number = 'The phone number you purchased from TeleSign goes here.'

url = "https://rest-ww.telesign.com/v2/voice"

payload = {
            "jsonrpc": "2.0",
            "method": "dial",
            "params": {
                "to": destination_number,
                "caller_id_number": caller_id_number

headers = {
    'Accept': "application/json",
    'Content-Type': "application/json",
    'Authorization': "Basic {}".format(b64encode(customer_id + ":" + api_key).decode('utf-8')),

response = requests.request("POST", url, data=json.dumps(payload), headers=headers)

  1. TeleSign notifies you with a dial_completed event. You should have some code to check the status is answered.

  2. If everything looks good, you move ahead and respond to the answered event with a request for the action of playing a message and collecting digits. Here is an example of what the payload of that request might look like:

  "jsonrpc": "2.0",
  "method": "play",
  "params": {
    "url": "https://url-pointing-to-audio-file.com",
    "collect_digits": {
      "max": 5,
      "timeout": 10000,
      "inter_digit_timeout": 3000,
      "terminators": "*"

Here is a code example showing how you might handle the event sent by TeleSign:

Play and Collect Digits in Python

from json import dumps, loads

from bottle import route, run, request, post

# This is a an example response to a dial_completed event that will play a message and collect digits during play.
# {
#   "jsonrpc": "2.0",
#   "method": "play",
#   "params": {
#     "url": "https://url-pointing-to-audio-file.com",
#     "collect_digits": {
#       "max": 5,
#       "timeout": 10000,
#       "inter_digit_timeout": 3000,
#               "terminators": "*"
#     }
#   }
# }

class Response:

    def __init__(self, method, params=None):
        if params is None:
            params = {}

        self.json_rpc = "2.0"
        self.method = method
        self.params = params

    def to_json(self):
        return dumps(self.__dict__)

def telesign_event():
    # Throughout a call session TeleSign will notify you of all events.
    # Each event requires you to send us an appropriate action defined in our documentation.
    # This endpoint needs to match the URL stored in our system to properly communicate.
    # In this example, the server will respond to the dial_completed event.

    # First extract the event from the JSON body in the request.
    event = request.json.get('event')

    if event == 'dial_completed':
        # Check for an 'answered' status. For 'answered' fill out your parameters: 
          url = "https://url-pointing-to-audio-file.com" # This is your message you want to play. 
          max = 5 # This is the maximum number of digits you want to collect.
          timeout = 10000 # How long to wait for the first digit before ending collection. 
          inter_digit_timeout = 3000 # How long to wait for the next digit before ending collection, after at least one digit has been entered. 
          terminators = "#" # The characters to use as terminators for end user entry of digits.

        # Generate the command in the JSON format used by TeleSign.
        return Response(method='play',
                                'url': url,
                                'collect_digits': { 'max': max, 'timeout': timeout, 'inter_digit_timeout': inter_digit_timeout, 'terminators': terminators }

        return Response(method='hangup').to_json()

run(host='localhost', port=8080, debug=True)

For a diagram, refer to the Set up the Call section of the Make an Outbound Call page.

  1. If playing the message and collecting the digits is successful, you get back the play_completed event from TeleSign. You can issue a request to hangup the call with hangup or you can send further messages by issuing additional play or speak commands.

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