1. A dynamically reconfigurable time-space-time switching system for use in conjunction with a high speed transmission media which conveys a plurality of channels of data within a repeated frame, comprising: a plurality of digital switching units each connectable to said transmission media and comprising; a first line terminating unit connected to receive said channels of data from said high speed transmission media; a TST switch connected to receive said channels of data from the first line terminating unit at the inlet ports thereof; a second line terminating unit connected to receive said channels of data from the outlet ports of said TST switch and transfer said channels of data to said high speed transmission media for transmission to another one of said switching units; a programmable fractional divider connected to clock said second line terminating unit; the frames of said channels of data having at least one timing adjustment interval; and means for measuring at least one timing adjustment interval within frames of said channels of data received at said first line terminating unit from said other switching unit, and for transmitting a control command to said other switching unit to adjust the rate of a counter at said other switching unit as a function of said measured timing adjustment interval, whereby said timing adjustment interval is maintained within a predetermined range.