OTTAWA—The country’s two biggest provinces won’t take part in what was supposed to be a nationwide testing of Canada’s Alert Ready system on Wednesday.

Public Safety Canada says it received notifications last week from Ontario and Quebec that the provinces are opting out of the testing because neither wants to send unnecessary alert tones to residents dealing with historic flooding.

The alerts sound when emergency officials send signals to cellphones, TV consoles and radio stations.

System operators are mandated to conduct nationwide testing of the service twice annually, blasting out distinctive electronic tones on LTE-enabled wireless devices that have their speakers turned on, as well as through television and radio.

Provinces and territories that are part of the system can opt out of the testing if they think it can be too disruptive during a real emergency.

The system has been in wide use for about a year, alerting Canadians about potential dangers, including natural disasters, biological and terrorist threats and civil emergencies.

It has also been used to issue localized Amber Alerts when police seek the public’s help in locating missing children, although there have been complaints from wireless users that the alerts have been issued too broadly.

A glitch in the public-alert system when it was first tested a year ago affected mobile devices across Quebec. An official with Canada’s telecom regulator said at the time that a coding issue originated with emergency-management officials in that province and Pelmorex Corp., which operates the system.

Testing on Wednesday is scheduled to be conducted at 10:55 a.m. local time in New Brunswick and Newfoundland, 10:25 a.m. in Labrador, 12:55 p.m. in Prince Edward Island and at 1:55 p.m. in Alberta, British Columbia, Manitoba, Nova Scotia, Saskatchewan, the Northwest Territories, Nunavut and Yukon.

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