The accord came at talks between South and North Korean members of a committee tasked with reopening the shuttered Kaesong joint industrial zone, the South's unification ministry said.
The committee was formed under a crucial agreement last month to resume operations at the zone.
The committee has focused on the timing for reopening the complex, with its sub-committee members handing technical and other issues.
"At today's sub-committee meeting, both sides agreed to make a test call through the military communication line on Friday," a unification ministry official told AFP.
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It was cut amid soaring military tensions that followed the North's February nuclear test.
North Korea had promised to reconnect the line in July but had not translated its words into action.
Currently, the two sides use a Red Cross hotline in the truce village of Panmunjom to exchange messages.
Kaesong, which was established just over the North Korean side of the border in 2004 as a rare symbol of inter-Korean cooperation, had come through previous crises on the Korean peninsula unscathed.
But in April, Pyongyang effectively shut down operations by withdrawing the 53,000 North Korean workers employed at the 123 South Korean plants.
As part of the agreement, the North accepted the South's demand that Kaesong be opened to foreign investors -- a move seen by Seoul as a guarantee against the North shutting the complex down again in the future.