Nortel Networks DCT1900 - Manual (Page 38)

Technical Product Manual - DCT1900
System Description, Hardware Building Blocks
3-2 System-DCT1900/R8/mw
© 2000-2005
Message Service (SMS) source. The printer can print a hardcopy of the system error messages.
In a multiple system configuration, up to 13 RE’s can be cascaded together.
The RE consists of:
z –One to four Modular Cabinets. The 10 inch Modular Cabinet contain a MCCB and a
backplane with 9 system board connectors, a rectifier circuit and a DC/DC converter.
z –A number of system boards.
The Modular Cabinet requires an external power source of -48Vdc.
3.2 Base Stations
The Base Station enables radio communications between the RE and Portable Telephones.
The Base Station has two main functions:
z To modulate a carrier with the digital encoded information (TDMA frame directed to Portable
Telephone),
z To demodulate a modulated carrier (TDMA frame received from Portable Telephone).
A Base Station communicates with the RE via two (2B+D) interfaces, requiring two twisted pair
cables. The two 2B channels (256 kbit/s) provide eight 32 kbit/s speech paths between a Base
Station and a RE, enabling a Base Station to handle eight simultaneous calls. In addition to data
communication, these two twisted pairs are also used to distribute power to the Base Stations.
One or two additional pairs can be wired to provide a longer powering distance.
Two methods exist to power Base Stations:
z Via local power supply.
z Via Modular Cabinet.
With the first method, Base Stations are powered by -48Vdc which is not routed via the cabinet.
The maximum cable length between Base Station and RE is only data limited and may reach up to
11,500 ft.
With the second method, power is distributed via the Modular Cabinet and Base Station cabling.
The cable length between the Base Station and cabinets now depends on the number of twisted
pairs used for power, the type of cable and environmental noise.
The number of Base Stations used in a system depends on the area to be covered and the traffic
density. Typical in–house coverage is a 100-200 ft. radius. The cell size may vary between 40 ft.
indoors and up to 1,000 ft. outdoors.
The air interface conforms to PWT MAC Layer and FCC part 15.
3.3 Portable Telephones
The Portable Telephone (PT) supports the basic functions of a normal wired DTMF–type
telephone. The PT is available in three models: the 9p23, the DT600 and the DT620. Each is
equipped with a 3-line 12 character dot matrix LCD display, backlit illumination keypad and display,
and plastic keypad. See Section 3, "Product Specifications," Chapter 1, "Portable Telephones"
and Chapter 12, "Portable Telephone Accessories" for further information. With the DLU, the 9p23
and DT620 PT will support up to 4 line appearances.