Panasonic Digital Business System - Overview
April 1997
Issue 6
6
Cabling Requirement
The cabling between the Central Control Unit (CCU) and each extension is 2 wire, 0.5mm
diameter copper conductor and terminated with a Line Jack Unit (LJU). Use a master LJU for
analogue extensions and a slave LJU for the digital extensions.
The following table shows the maximum cable length from the CCU.
Cabling from the Network Test and Termination Point (NTTP) must also comply with these
requirements.
Table 7 - Maximum Cable Distances
Over-voltage Protection
Surge arresters are fitted to the PAS, ITS and 1AS ports of the system. If the extension
cabling extends between buildings or runs around the outside of a building, surge arresters
should be fitted at both exit and entry points.
PBX Recall
The DBS can be installed as a host or subsidiary system to suitably approved PBX
equipment.
As a host the DBS will accept timed break recall signals from a PBX connected to a 1AS
port.
As a subsidiary the DBS can provide both timed break and earth recall signalling to the host
from PAS ports.
1AS Port Line Feeding
The DBS is not a through fed system. Line feeding from 1AS ports to connected equipment is
derived internally from the DBS CCU. The maximum current that can be supplied to
extension equipment on 1AS ports is 50mA.
Analogue Extensions
When using separately approved extension apparatus, Panasonic recommend DTMF
signalling. The recall signalling must be timed break. The impedance class of the apparatus
must be class (a) of clause 4.3.2.1 of BS6305:1982.
Cable
Maximum Loop Resistance
Maximum Length
CCU > ITS
40 ohms
240m
CCU > DSS
20 ohms
120m
CCU > 1AS (A version)
100 ohms
480m
CCU > 1AS (B version)
100 ohms
880m
CCU > PFU
250m
NTTP > CCU
15m