Specifications

13–1
Chapter 13. G.703
13.1 G.703
G.703 data is either in AMI, B8ZS (8 zero) suppression, or HDB3 (3 zero) suppression
formats. There is not a coexisting clock that is on a separate line for G.703 data. The
clock is derived from the data stream within the modem and in the user equipment. Loop
timing, if desired, must occur in the customer equipment for the link to operate in
Master/Slave. The modem cannot do loop timing in G.703 operation because the modem
does not emit an ST signal for the Transmit Clock Source modem can be placed in loop
timing under EIA-422 or V.35 operation. Therefore, a master/slave relationship easily
occurs. This causes the receive clock to be placed on the ST line to the terrestrial equipment.
The customer equipment can then clock the transmit data to the modem using the ST line
that has been derived from the RX recovered clock.
13.1.1 G.703 Specifications
Table 13-1. G.703 Specifications
Parameter Specification
Primary Data Circuits Supported T1 SD, RD
E1 SD, RD
Interface Type Transformer coupled symmetrical pair
Data Rates T1 1544 kbps ± 100 bps
E1 2048 kbps ± 130 bps
Pulse Width T1 324 ± 50 Ns
E1 244 ± 25 Ns
SD Amplitude
T1 3V +0.3/-1.5V-pk into 100Ω
E1 3V +0.3/-1.5V-pk into 120Ω
RD Amplitude
T1 3V +0.3/-1.5V-pk into 100Ω
E1 3V +0.3/-1.5V-pk into 120Ω
Pulse Mask T1 G.703.2
E1 G.703. 6
Jitter Attenuation T1 G.824
E1 G.823
Line Code AMI, B8ZS, B6ZS, HDB3