But inside what was once a library, it's a hive of activity. Slices of banana cake are being passed around, mugs of tea and instant coffee are in high demand and the phones, despite the early hour of the morning, don't stop ringing.

This is the front line of the fight against suicide. Ten people are rostered on to the Lifeline call centre in Sydney this morning and there are similar numbers in Parramatta and Brisbane.

They will be taking calls from anywhere in Australia from people in desperate circumstances.

Calls to Lifeline, the suicide prevention service, are normally expected to last between 15-25 minutes. If a telephone crisis supporter takes longer they risk blocking someone else who might not be minded to hold.

Dee, in one of the partitioned sections, takes  an interstate call at 3.53am from a schoolgirl who says she's 15 - and is still engrossed at 4.37am.

"What sort of tablets do you have? Are they sleeping tablets?"

To protect the caller's privacy her answers can't be heard so this is just one side of the exchange.

"What year are you in?...Year nine?

"Your parents are pressuring you too much to do well at school? Have you been able to talk to your mum at all? ... You don't talk [to her] much.

"I would think your mum would be really upset about how you are feeling. She doesn't care ...

"Have you got rid of the tablets? Are you feeling a bit safer now?"

Robyn is in a partitioned booth opposite handling another crisis.

"I can hear you are so upset. You are tired of struggling. You understand if you choose to die tonight there would be no one to care for your dogs and cats? I can hear how betrayed you are by your daughter. Right now, as you have said, it is going down hill really quickly."

The importance of pets to people in this situation cannot be underestimated. Many callers live in isolated locations and are lonely. Desperately lonely. A pet can bring with it the reason and responsibility to live.

Caroline, one of the supervisors (their real title is "in-shift support"), says: "Animals are great. When we know someone has got a pet it is really something to work with."

This is the night after the Queen's birthday public holiday.

The call centre is on the north shore, one of the three call centres open overnight with paid crisis supporters. At 4am the other two shut down and all calls for the country for the last two hours of the shift are directed here.

The 10 crisis supporters aren't on double time for working after a public holiday but there are warm sausage rolls to help get them through the night. Answering calls like these takes a toll. Then there are the sex callers to weed out. For those they press the Malicious Call ID button which might provide a trace.

They can take half an hour's break but many don't bother. Others get some benefit from just washing their face and hands to freshen up. One or two slip into meditation for a few minutes. Whatever works.

Two supervisors hover around those fielding the calls to keep an eye on things. If suicide emerges as an issue the staffer will ring a bell or wave an arm and a supervisor is there. A call can be traced and an alert passed to state police headquarters for wherever the call is sourced. Lifeline doesn't call ambulances. Often the police say they will investigate and the outcome remains unknown. Sometimes the people will call back. Sometimes the news is that they got there just in time.

Dee wraps up the call to the schoolgirl at 5am. "Talk to a teacher. I know it will be awkward but you will be able to trust her. You look after yourself and stay safe tonight. Big breath. Goodnight doll."

Dee lifts her head, having replaced the phone.

"I had her the other night. She took an overdose a couple of months ago. She's really lovely. It was a good call. I am aware of getting too close to her. The danger is of her calling every night and asking for me. She is suicidal but she's a lot more settled. She was a lot calmer."

Eleanor, the supervisor, asks Dee if she's OK. It was a mammoth call.

"OK. A bit drained," is the reply.

It's 5.50am and outside the first light is starting to break through. A few minutes later Dee's phone rings again.

"Hello, this is Lifeline."

She logs the call typing in that it's a woman saying she's in her early 20s and from Perth.

"I can hear that you are really struggling at the moment. Just take a deep breath," she says.

"It sounds like you have got an awful lot on your plate. It must be pretty scary for your mum thinking that she might lose you..."