The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment. E1/T1 is based on this technology. In many places it is now being replaced with SDH. The line rate of a T1 line is 1.544 Mbit/s. T1 format carries 24 pulse-code modulated, time-division multiplexed speech signals each encoded in 64 kbit/s streams, leaving 8 kbit/s of framing information which facilitates the synchronization and demultiplexing at the receiver. T1 is used in North America. E1 is used in Europe. The line rate is 2.048 Mbit/s which is split into 32 time slots, each being allocated 8 bits in turn. One timeslot (TS0) is reserved for framing purposes and another (TS16) is often reserved for signalling purposes, to control call setup and teardown according to one of several standard telecommunications protocols. This includes Channel Associated Signaling (CAS) where a set of bits is used to replicate opening and closing the circuit, or using tone signalling which is passed through on the voice circuits themselves. RADCOM has a wide range of products that support technologies running on E1/T1 interfaces. | 
