The party line on a particular issue is the official view taken by a political party, which its members are expected to support. They ignored the official party line. the official opinion of a political party or other organization, which its members are expected to agree with and support follow/toe the party line (=to support the official opinion)
Party lines, in the UK, were where two customers shared one line They both had different numbers and the telephones rang independently of each other If both picked up their handsets at the same time, then both could hear the conversation Only one call could be made at any one time To make a call the user would press a button on the telephone to get dial tone
a telephone line shared by multiple residences; a one-pair circuit that can have as many as 8 phone numbers; only one person can use the line at a time