ne systems and peripheral systems, as well. Their intent is not SO much to get into the telephone system business, but rather to enable their customers to experiment with applications that use capabilities of both the telephones and the computer networks, such as having a screen of customer information pop up on the computer with the arrival of a call from that customer called a screen pop. INTERCOM COMPANIES The office telephone system did not always provide the ca- pability for calling others in the same office, now known as in- ternal calls. There was once a larger group of companies that sold intercoms for inter-office communications. Several of these companies still remain since there are some environments like a Wall Street brokerage trading room, that demand instantaneous voice communications with other individuals in the same office or same large room. The intercoms are separate desktop devices with their own control equipment for the backroom and using their own sepa- rate pairs of wires on the office cabling infrastructure. WIRELESS TELEPHONES WITHIN THE OFFICE As some office workers move around the workplace for most of the day, there is an increasing need for them to be able to continue to receive their calls. Some manufacturers of telecommunications systems also sell wireless telephones or wireless headsets to work with that sys- tem, using base stations, with the same concept as many wireless telephones used in the home. These tend to be comparatively high priced and work within a limited area. Several companies manufacture separate wireless systems for the office environment requiring the installation of transmitters in the ceiling enabling coverage of the entire office. These systems The Telecom Handbook 3 291 UNDERSTANDING THE INDUSTRY are separate from the office telephone system but can be set up to work in conjunction with it, enabling workers to receive calls to their desktop telephone from anywhere in the office. The drawback of these systems is that they tend to cost as much as the telephon