Spok Holdings, Inc. is a holding company. The Company, through its indirect subsidiary, Spok, Inc., provides critical communication solutions for enterprises. The Company offers critical communication for healthcare, government, public safety and other industries. The Company's segment is critical communication business. It offers paging services and selected software solutions in the United States and abroad, generally in Europe, Canada, Australia, Asia and the Middle East. The Company offers its services and products primarily to three market segments: healthcare, government and large enterprise. It also offers implementation services for its products. The Company offers subscriptions to one-way or two-way messaging services for a periodic (monthly, quarterly, semi-annual, or annual) service fee. A subscriber to one-way messaging services select coverage on a local, regional or nationwide basis as per their messaging needs. Two-way messaging is offered on a nationwide basis.