Spok Holdings, Inc., through its wholly owned subsidiary Spok, Inc., is engaged in healthcare communications. It is focused on offering a suite of unified clinical communication and collaboration solutions, which includes call center operations, clinical alerting and notifications, one-way and advanced two-way wireless messaging services, mobile communications, and public safety solutions. It offers its services and products to three market segments: healthcare, government, and large enterprises. It provides one-way and advanced two-way wireless messaging services, including information services, throughout the United States. These services are offered on a local, regional and nationwide basis, employing digital networks. It offers voice mail, personalized greetings, message storage and retrieval, and equipment loss and/or maintenance protection to both one-way and two-way messaging subscribers. These services are commonly referred to as wireless messaging and information services.