Back-up systems had to be used in the north east of Scotland after the Scottish Fire and Rescue Service was hit by a radio communications failure.
Mobiles and radios were used to keep in touch with the North operations control centre in Dundee.
The issue last weekend was identified as a networking fault.
SFRS area manager Mike Dickson said: "As of 7 August, a permanent solution was put in place which ensures that this problem should not occur again."
The Fire Brigades Union (FBU) has called for an investigation.
The issue was between Friday 4 August and Monday 7 August.
Mr Dickson said: "The Scottish Fire and Rescue Service's Dundee operations control centre noted an issue with radio communications in the North Service Delivery Area.
"Thanks to robust strategic planning and the professional training of our control staff, there was no loss in communication with SFRS resources and no effect on the service's ability to respond to emergencies.
"All SFRS control rooms are equipped with backup radio and telephone communications equipment which can be immediately activated in the event of an issue arising - this was used in this instance to ensure that there was no loss in communications.
"Fire officers equipped with personal issue radios strengthened this contingency plan."
FBU regional official Denise Christie said: "We were made aware by some members of the radio failures for the whole weekend.
"They had to rely on mobile telephones to contact crews who were mobile out with their fire stations.
"We believe the loss of communications did affect the service's ability to respond to emergencies."
She added: "We are asking the fire service to have a thorough investigation."