| Pulse code modulation (PCM) of voice frequencies | |
 | |
| Status | In force |
|---|---|
| Year started | 1988 |
| Latest version | (04/16) April 2016 |
| Organization | ITU-T |
| Related standards | G.191,G.711,G.729 |
| Domain | audio compression |
| Website | https://www.itu.int/rec/T-REC-G.703 |
G.703 is aITU-T standard originally written in 1972[1] but subsequently revised a number of times since. It defines a physical and electrical interface used for encoding voice or data over 75ohm co-axial cable terminated inBNC or Type 43 connectors or 120ohm twisted pair cables terminated inRJ48C jacks. The choice is carrier- and region-dependent.[2]
G.703 defines digital carriers of various speeds such asT1 andE1. These are organised as part of a hierarchy of carriers defined in G.702.
A G.703 E1 link is typically, though not necessarily, framed using the G.704 standard which divides the data stream into time slots. Typically, each time slots represents an E0 (64 kbit/s) voice channel encoded usingpulse-code modulation (PCM). The PCM coding is defined in theG.711 standard. G.704 also includes a control timeslot slot and a signalling timeslot (CAS or CCS).
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