((a)) ** .—** Except as provided in subsection (b), this chapter applies to any contract or bid specification for a contract, whether negotiated or advertised, that—
((1)) is made by the Federal Government or the District of Columbia;
((2)) involves an amount exceeding $2,500; and
((3)) has as its principal purpose the furnishing of services in the United States through the use of service employees.
((b)) ** .—** This chapter does not apply to—
((1)) a contract of the Federal Government or the District of Columbia for the construction, alteration, or repair, including painting and decorating, of public buildings or public works;
((2)) any work required to be done in accordance with chapter 65 of this title;
((3)) a contract for the carriage of freight or personnel by vessel, airplane, bus, truck, express, railway line or oil or gas pipeline where published tariff rates are in effect;
((4)) a contract for the furnishing of services by radio, telephone, telegraph, or cable companies, subject to the Communications Act of 1934 ( et seq.);
((5)) a contract for public utility services, including electric light and power, water, steam, and gas;
((6)) an employment contract providing for direct services to a Federal agency by an individual; and
((7)) a contract with the United States Postal Service, the principal purpose of which is the operation of postal contract stations.