Random call

"Mr. Watson - come here"

The first telephone call is usually dated to 10 March 1876, when Alexander Graham Bell, in a Boston workshop, spoke into his transmitter and his assistant Thomas Watson heard him in the next room. Bell's preferred greeting for answering the new device was "Ahoy". It was Thomas Edison who pushed for "hello" instead, and Edison won - which is why, a century and a half later, almost every call in the world still begins with a word that was barely a greeting before the telephone.

For decades, every call was connected by hand. In 1878 Emma Nutt became the first woman hired as a telephone operator, in Boston, and for years switchboards like the one above were run by operators who plugged a cord into one jack and then another to join two strangers' lines. The automatic exchange came later: Almon Strowger, a Kansas City undertaker, patented his automatic switch in 1891 - according to the story he liked to tell, because he suspected a local operator of putting his customers through to a rival.

How a random call is connected today

TalkLive is a switchboard with the operator taken out and the phone numbers taken away. When you tap to talk, your browser joins a queue of people searching at the same moment. When another adult is available and your settings are compatible, TalkLive connects you - and then gets out of the way, letting your two browsers carry the conversation themselves.

The technology underneath is WebRTC, an open standard built into every modern browser. Many networks - mobile carriers, offices, university Wi-Fi - block direct connections between devices. When that happens, the call is relayed through TalkLive's TURN server instead. Either way, the audio is encrypted in transit and neither route records it. The Journal walks through the whole process in what happens in the two seconds after you press Start.

Because this is ordinary internet traffic, a call to someone across the world costs exactly the same as a call to someone across the street: nothing beyond your normal data.

How much data does a call use?

Voice is compressed with Opus, an open codec standardised in 2012 and designed for speech over unreliable networks. It adapts to your connection, squeezing harder when the signal is weak. In practice, a voice-only call is one of the lightest real-time things you can do online.

If you are on a limited mobile plan, voice is the cheapest way to have a live conversation online, and switching to text costs almost nothing.

When the line is bad

Most call problems are one of five things, and all five have quick fixes.

• No microphone prompt, or "permission denied"Open your browser's site settings for talklive.app, set Microphone to Allow and reload. On iPhone and iPad, also check Settings, then your browser, then Microphone.
• You hear them, they cannot hear youAnother app may be holding the microphone. Close other calling or recording apps, and check the right input is selected if you use a headset.
• EchoUse headphones. Echo almost always means the other person's voice is coming out of your speaker and back into your microphone.
• Choppy or robotic soundA weak connection. Move closer to the router, or switch between Wi-Fi and mobile data.
• Silence on both sidesTap Next. Very restrictive networks occasionally block even relayed calls; changing network usually fixes it.

Answering a call you did not plan

A random call is spontaneous on both ends, so give the other person a second to settle - they may still be putting headphones in. Start with your hello (Edison would approve) and a quick "can you hear me okay?". Mute yourself if you need to step away rather than leaving someone listening to your television. If the call is not going anywhere, Next ends it for both of you and starts a new search; Hang Up stops calling altogether.

Keep it a call between strangers: no surname, address, workplace or social handles in the first conversation, and never money or codes for anyone. Every call has Report and Block, and blocked people are never matched with you again. If calls make you nervous in general, you are in good company - why your heart races when the phone rings is a gentle place to start. And if you would rather not use your voice at all, text chat needs no microphone.