Timing recovery apparatus

The use of synchronous residual time stamping for timing recovery depends upon there being a common network clock at the two ends of an asynchronous transmission mode connection and the basic technique is not suitable for use between terminals in different timing domains. Other techniques for timing recovery are available but they introduce wander or have other drawbacks in terms of practicality, cost, or the use of network resources. The timing recovery apparatus is placed at timing domain boundaries and provides a means for extending the use of synchronous residual time stamping into a new timing domain. The apparatus includes means for calculating a value indicative of the number of complete source network clock cycles in a predetermined time period which is loaded into a counter. When the counter reaches a predetermined value a latch connected to a further counter contains a new residual time stamp value.