Result: standard mapping
How many DS0s are in an E4?
An E4 carries 1,920 DS0s, per ITU-T G.702 and ITU-T G.704.
1,920
DS0s in an E4
Working
E4 → 64 × E1 → 30 × E0 → 1 × DS0
- 64 × E1 in each E4 ITU-T G.70264 E1s, which is 4 E3s × 16 E1s.
- 30 × E0 in each E1 ITU-T G.70430 voice channels in 32 timeslots. TS0 is framing and TS16 is channel-associated signalling.
- 1 × DS0 in each E0 ITU-T G.702E0 and DS0 are each one 64 kbit/s PCM channel.
- 64 E1s
- 64 × 30 = 1,920 E0s
- 64 × 30 × 1 = 1,920 DS0s
Leftover capacity
16.384 Mbit/s of each E4 line rate (139.264 Mbit/s) sits outside 1,920 × 64 kbit/s of DS0 line rate (122.880 Mbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.
By bit rate only
Dividing the line rates gives 2,176, which floors to 2,176 DS0s by bit rate only. The standard mapping is 1,920. Use the mapping.