H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
H04J3/1605—Fixed allocated frame structures
H04J3/1623—Plesiochronous digital hierarchy [PDH]
H04J3/1647—Subrate or multislot multiplexing
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04M—TELEPHONIC COMMUNICATION
H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
H04M11/002—Telephonic communication systems specially adapted for combination with other electrical systems with telemetering systems