Result: standard mapping
How many E0s are in an OC-12?
An OC-12 carries 7,560 E0s, per Telcordia GR-253 and ITU-T G.704.
7,560
E0s in an OC-12
Working
OC-12 → 12 × OC-1 (STS-1) → 21 × E1 → 30 × E0
- 12 × OC-1 (STS-1) in each OC-12 Telcordia GR-25312 × OC-1 (STS-1). Channelized OC-12 is 12 STS-1s.
- 21 × E1 in each OC-1 (STS-1) Telcordia GR-253Seven VT groups × three VT2 (E1).
- 30 × E0 in each E1 ITU-T G.70430 voice channels in 32 timeslots. TS0 is framing and TS16 is channel-associated signalling.
- 12 OC-1s
- 12 × 21 = 252 E1s
- 12 × 21 × 30 = 7,560 E0s
Leftover capacity
138.240 Mbit/s of each OC-12 line rate (622.080 Mbit/s) sits outside 7,560 × 64 kbit/s of E0 line rate (483.840 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 9,720, which floors to 9,720 E0s by bit rate only. The standard mapping is 7,560. Use the mapping.