How To get real-time transcriptions and insights in a Telephone call using Symbl SDK

Realtime Output with PSTN Dialing using Voice SDK#

In this example let's walk through how to get the real-time transcription and insights events in a Telephone call.

The code is available here:

Getting started#

View on Github

Open .env file and add your APP_ID, APP_SECRET, SUMMARY_EMAIL. You can get APP_ID and APP_SECRET from

We will use symbl-node package:

const {sdk} = require('symbl-node')

Let's start by initialising symbl-node sdk:

await sdk.init({
appId: process.env.APP_ID,
appSecret: process.env.APP_SECRET,
basePath: '',

Now let's start our connection:

const connection = await sdk.startEndpoint(endpointConfig)

First of all let's provide phone number and endpoint type:

endpoint: {
type: 'pstn',
phoneNumber: process.env.DEFAULT_PHONE_NUMBER,

In case you want to use sip connection, you can use type: sip and provide SIP URI to dial-in to. This should be unique for an active call/meeting in your system. You can also provide dtmf code if you have one. You can find this code on meeting platform invite. You can leave it blank if not connecting to meeting platform

dtmf: "<code>",
type: 'sip',
uri: ''

You can also pass custom audioConfig. If not provided, it uses PCMU with 800 sample rate. If you want to provide it, you can do it like so:

audioConfig: {
encoding: 'OPUS',
sampleRate: 48000

Symbl provide various insights from the call. Main insights categories are question and action_item. In order to include insights in processing, you need to specify them in configuration like so:

insightTypes: ['action_item', 'question'],

You can specify different actions to happen during the call. We will define just one:

actions: [
invokeOn: 'stop',
name: 'sendSummaryEmail',
parameters: {
emails: [process.env.SUMMARY_EMAIL], // Add valid email addresses to received email

When our connection will be stopped, Symbl will send summary mail provided in .env file

Let's also name our session by providing:

data: {
session: {
name: 'My Test Meeting',
Getting connection Id.#

For subscribing to the data, we will need to use connectionId unique to each active connection. to get it you can simply retrieve it from connection response:

const connectionId = connection.connectionId

Sending speaker events.#

We can send different speaker events to our connection indicating that different speakers started speaking. That will give us more personalised insights and get better meeting summary

In our example we will do it by calling helper getScheduleEvent function, that we will review in a bit. We pass SpeakerEvent type to it by using SpeakerEvent.types enum from symbl-node, passing user data and timestamp:

const scheduleEvent = getScheduleEvent(sdk, connectionId)
setTimeout(() => {
// Schedule all the events to be sent.
scheduleEvent(SpeakerEvent.types.startedSpeaking, users.john, 0)
scheduleEvent(SpeakerEvent.types.stoppedSpeaking, users.john, 5)
}, 1000)

We retrieve users just from the global array of users but in real world example that might be users data retrieved from database:

const users = {
john: {
userId: '',
name: 'John',
mary: {
userId: '',
name: 'Mary',

In order to push event to our connection we will create an event like so:

const speakerEvent = new SpeakerEvent({
type: eventType,
speakerEvent.timestamp = new Date().toISOString()

And push it using pushEventOnConnection function provided by SDK:

sdk.pushEventOnConnection(connectionId, speakerEvent.toJSON(), (err) => {
if (err) {
console.error('Error during push event.', err)
} else {
console.log('Event pushed!')

Realtime insights#

In order to get real time data, we need to subscribe to the connection. We can do so by using:

sdk.subscribeToConnection(connectionId, (data) => {})

data has type field, so we will check for transcript_response, insight_response and message_response

transcript_response are our real-time transcriptions that we want to preview in the console:

if (type === 'transcript_response') {
const {payload} = data
process.stdout.write('Live: ' + payload && payload.content + '\r')

Transcripts are changing all the time, but once they are processed into reasonable message and not just words, we will get message_response with messages array:

if (type === 'message_response') {
const {messages} = data
messages.forEach((message) => {
process.stdout.write('Message: ' + message.payload.content + '\n')

And finally if there will be any question or action item during conversation, you will get insight_response:

if (type === 'insight_response') {
const {insights} = data
insights.forEach((insight) => {
process.stdout.write(`Insight: ${insight.type} - ${insight.text} \n\n`)

As you can see with this data there is a wide array of implementations you can do.