Plan type descriptions
Plan 1
One entrance panel serving any number of telephones.
Plan 2
One entrance panel serving any number of telephones plus intercommunication with a resident porter.
Plan 3
One entrance panel serving up to 10 telephones with internal intercom facility.
Plan 21,22,23
As Plan base but with a second entrance served.
Plan A
Internal intercom with up to 10 telephones. There is no entrance unit.
Plan B
Internal intercom system between a porter's telephone and a number of telephones. There is no entrance unit.