Apache Reference: http_core, KeepAliveTimeout

KeepAliveTimeout

Set the Timeout for HTTP Keep-Alive Connections
Syntax: KeepAliveTimeout A
Example: KeepAliveTimeout 120
Since: Apache 1.1

This directive sets the number of seconds that the server will wait for a subsequent request on a Keep-Alive connection before closing it. Once a request has been received, the timeout value specified by the Timeout directive applies.