BT confirms that 50,000 homes from Pentland in the Highlands to the Orkney Isles were unable to contact the police, fire, ambulance and coastguard crews, who in turn couldn't communicate with each other.
The breakdown, which lasted for two-and-a-half hours, is being blamed on a "rare computer fault" at BT's main Inverness Cameron exchange, which knocked out 100 other smaller exchanges.
Despite an emergency line being set up by the Scottish Office to provide communications between the emergency services, they were still reduced to using radio links to guarantee communications.
While not on the same scale as the recent breakdown in freephone and local call numbers used nationally, this latest failure will put a greater focus on the type of switching and routing equipment BT has installed in its public networks.
The national failure, which lasted more than 24 hours, was also publicly blamed on "a computer fault". BT now admits that it was caused by a switch from a supplier which BT chose not to name. The same supplier is believed to be involved in this latest glitch.