Evidence regarding communication between the NSW Police Commissioner and his deputy during the Sydney siege suggests he was aware of technical problems with intelligence-gathering equipment, an inquest has heard.

Deputy Commissioner Catherine Burn has told the Sydney siege inquest she did not recall until this morning receiving a text message during the ordeal from Commissioner Andrew Scipione about requesting technical equipment.

Deputy Commissioner Burn has been under sustained questioning about text messages she received and deleted during and after the siege.

The inquest has previously heard Deputy Commissioner Burn had deleted her text messages from the night and police were not able to retrieve them.

But today it was revealed she had copied a text from Commissioner Scipione and emailed it to herself at 10:37pm on the night of the siege in December 2014.

Counsel assisting the inquest Jeremy Gormly said the email containing the text said Commissioner Scipione had spoken to the Special Services Group (SSG) about the role technical equipment had played on the night of the siege.

Mr Gormly asked Deputy Commissioner Burn to read the email out loud.

"It has become apparent we should be preparing a fresh bid for any new equipment that is necessary," Deputy Commissioner Burn read from the email.

"I will need this soon to ensure we are appropriately prepared for the future."

This included electronic and audio intelligence-gathering equipment, the inquest heard.

The inquest has previously heard there were technical challenges for NSW Police during the siege including a delay of up to five minutes on transmissions from a covert listening device that officers had planted in the Lindt Cafe.

This resulted in a critical delay in the final moments before gunman Man Haron Monis shot cafe manager Tori Johnson and police stormed the cafe.

The Lindt cafe inquest is examining the deaths of three people, hostages Katrina Dawson and Mr Johnson, and Monis, who were killed during the siege at Sydney's Martin Place in December 2014.

The three most senior police officers in NSW are all facing the inquest this week to explain which operational decisions, if any, they made during the Sydney siege.

'Not my role' to assess resource issues: Burn

Deputy Commissioner Burn was questioned on how the request for the equipment related to the resourcing on the night.

She said she could not be sure whether the request from the Commissioner was in response to the transmission delays, but she said the equipment greatly enhanced the capability of the police force.

Philip Bolton SC, the barrister for Ms Dawson's family, later asked the Deputy Commissioner if she asked questions during the siege about resources and equipment.

"Did you actively inquire of your commanders to see if things were operating properly?" Mr Bolton asked.

Deputy Commissioner Burn replied: "No ... that is not my role."

"If there are resource issues, it's up to the police commander and the police forward commander to identify and rectify," she said.

"I was not informed by Police Commander [Mark] Murdoch that there were resourcing issues that were impacting on decision making."

Email a bit of a shock: Deputy Commissioner

Deputy Commissioner Burn said she had not recalled the email until she was shown it this morning.

"It was bit of shock," she said.

Deputy Commissioner Burn was questioned further by Mr Gormly as to whether she remembered sending or receiving the email.

"I don't recall it ... now that I am looking at it, yes."

The inquest heard the email was not in the initial bundle of correspondence Deputy Commissioner Burn provided to the inquest who said she was not aware if it was part of the correspondence that went to the police legal team.

Deputy Commission Burn said she had gone through her email vault with police IT specialists to recover all of her emails from the night and she could not explain why this one was not found.

When asked who checked and identified the email last night, she replied that officers from the NSW Police professional standards command had found it.

Burn did not think she needed to keep texts

Deputy Commissioner Burn was adviser to the state's crisis policy committee during the 2014 siege.

In her evidence on Monday, she said she gave no orders or directions to the operational commanders.

NSW Police Commissioner Andrew Scipione is set to face the siege inquest this week. ( AAP: Dan Himbrechts, file photo )

Deputy Commissioner Burn told the inquest she did not think she needed to retain her text messages and it was highly unlikely the texts dealt with the progress of operations.

Commissioner Scipione will also give evidence in the next few days.

The senior officers were set to give evidence a fortnight ago but their appearance was delayed as documents had not been provided to all the legal teams, including those representing the families Ms Dawson and Mr Johnson.

The families of Mr Johnson and Ms Dawson had lobbied for the Commissioner and his deputies to explain their actions on the night.

NSW coroner Michael Barnes is set to hand down his findings later this year.