Spok Holdings, Inc., through its subsidiary, Spok, Inc., provides critical communication solutions for enterprises. The Company is engaged in the healthcare communications. The Company is a provider of paging services and selected software solutions in the United States and abroad, on a limited basis, 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. 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 selects coverage on a local, regional or nationwide basis as per their messaging needs. Two-way messaging is offered on a nationwide basis. The Company's critical communication solutions are grouped under four product categories: Contact Center, Clinical Alerting, Mobile Communications and Public Safety.