Timing Cable Specifications For The E1 Unbalanced Circuit - Nortel Passport 15000 Hardware Description

124 Chapter 3 Shelf assembly
Timing cable specifications for the E1 unbalanced circuit
241-1501-200 5.2S2
• The Pulse Amplitude for balanced is at 3.0 V with peak "mark", a value
of 0 (zero) +/- 0.3 V "space" into 120 Ohms at the transmitter.
• Balanced is 120-Ohm twisted pair cable.
• At the receiver end at 1024 kHz, the maximum loss due to cables is 0 to
6 db.
• See the ITU-T G.703 Section 9 for other details with respect to pulse
mask, one's ratio, and other considerations.
The functional specifications for the E1 balanced receive (RX) circuit for a
120-ohm twisted pair of the A or B timing reference interface are
• two 475-ohm resistors for over-voltage protection on the ZPACK
connector
• two surface-mounted fuses for current protection on the network side
• a diode bridge for voltage protection
• 33-pF capacitors used as a high frequency filter for immunity to noise
• two 68.1-ohm resistors for matching impedance
• generally, a 1-to-1 step-up transformer is added to interface to the
transceiver
The E1 unbalanced BITS interface is the digital clocking source with the line
format called common channel signalling (CCS)- no signals or analogue
modes. Zero suppression is HDB3, CRC-4 is enabled. It must have the
following operational characteristics into the alarm/BITS module.
• The operating frequency is 2,048 kbits/s with a tolerance of +/- 50 ppm
or better.
• The Pulse Amplitude for unbalanced is at 2.37 V with peak "mark", a
value of 0 (zero) +/- 0.273 V "space" into 75 Ohms at the transmitter.
• Unbalanced is 75-Ohm coax cable.
• At the receiver end at 1024 kHz, the maximum loss due to cables is 0 to
6 db.