BusinessPhone Communication Platform 4.0
System Description ASB 150 02

## System Structure

### Block diagram

RASC |  | External computer for operation & maintenance |
PSTN |  | Public telephone exchange (network) |
PBX |  | Another private telephone exchange |
36 VAC |  | Transformer or switched mode power supply |

### Block description

#### Printed board assemblies (boards)

CPU-D_ |  | Board containing the central parts of the PBX's control system |
ELU-A |  | Board for connecting analogue telephones |
ELU-D_ |  | Board for connection of digital telephones DBC 6xx, DBC 2xx and DBC 199 |
ELU-C |  | Board for connection of (ASB 150 01) digital telephones, DBC 75x |
BS |  | The radio Base Station is connected to the IC-LU and establishes the radio link to the portables |
BTU-A |  | Board for "analogue" connection to the public telephone network or other telephone exchanges |
BTU-B |  | Board for "digital" ISDN connection to the public exchange and terminal equipment in the 2B+D format on up to 8 lines. |
BTU-C |  | Board for "analogue" tie and trunk line with current loop (DC-loop) to connect to other telephone exchanges or public networks incl. DID for some countries |
BTU-D |  | Board for "digital" connection 30B+D to the public exchanges. The board also contains register signalling equipment |
BTU-E |  | Board for "analogue" tie line with E&M signalling for connection to other telephone exchanges.The board also contains register signalling equipment for CEPT L1 and SSAC 15 |
CM |  | Call metering board is a daughter board to be installed on a BTU-A or -C for detection of 12/16 kHz and 50 Hz metering pulses |
IC-CU |  | Controls the DECT cordless system and interfaces to up to 4 base stations (only index2). In the ASB 150 02 system this board acts like an ELU board in the PBX |
FECU |  | Board controlling the number of portables allowed to be connected to the system |
IC-LU |  | Provides ADPCM conversion, handling of communication, echo cancelling and synchronisation of the Base Stations |
MFU |  | Multi function unit comprises 4 analogue extensions with 4 DTMF receivers, 8 digital extensions, 4 ISDN T/S- interfaces and a voice memory function similar to the VMU-HD with 4 registers and 4 voice channles. |
REG |  | Sub-equipped BTU-D, including only the register function |
VMU-D |  | Board for storage/playback of recorded messages and announcements |
VMU-HD |  | Board for recording/playback of messages and announcements stored on a PCMCIA flash disk and register function |
AUX_ |  | Board providing up to 3 V.24 interfaces to connect devices e.g. PC, printers. The AUX3 provides just 1 V.24 interface |
PUB6 |  | Back plane with rectifier, voltage converter and nine board positions supporting Integrated Cordless functionality. |

Note

The boards BTU-A, ELU-A and ELU-D are also available as sub-equipped boards with reduced number of interface lines.

#### Backplane busses

Clock bus |  | Clock signals and synchronisation signals for coordination of the system's subfunctions |
FC-bus |  | Function Control bus. Control of the connection of the individual boards to the backplane and restart of individual boards |
SC-bus |  | System Communication bus. Communication link between the system processors |
PCM-bus |  | Bus for voice connection between the individual devices, connected via the system switch. |

### Power distribution

The power to the PBX is supplied either by a transformer (36V AC) or a power supply with battery charger (48V DC).

Internally a number of voltages are created that are distributed via the PUB to all board positions:

- -48 VDC
- +12 VDC
- -12 VDC
- +5 VDC

Other voltages required on the boards are generated locally when they are needed (e.g. -5 VDC).

Some boards are equipped with an analogue/digital converter monitoring the local voltages and reporting the data to the operation & maintenance system. The CPU-D_ and AUX_ boards measure the voltages of the centrally distributed power.

### Clocks and synchronisation

The system clock is equipped with an oscillator (16,384 MHz) that can be synchronised with a master public telephone exchange via a digital line.

The program controls which digital trunk board shall be used as master, which then can be set up at installation. Synchronisation is continuously monitored and if sync is lost the new sync is extracted from another digital line if available.

The realtime clock is a completely separate function that keeps track of year, month, day, weekday, hours, minutes and seconds. Support for "day type", that is working day, day before holiday and holiday, is also included. The circuit has an internal battery, allowing the clock to function even if the PBX is shut down.

The clock generator on the IC-CU has a similar function as the clock input from the PSTN network and can be used to synchronise the exchange system clock. In this case the 4MHz, Frame sync., Multi frame sync. and Strobe are synchronised. The system clock is then received on the IC-CU to synchronise the radio Base Stations.

### Control system

CP |  | Central Processor, administers traffic (telephony facilities) and operation & maintenance functions |
RP |  | Regional Processor, administers the hardware/line interfaces on the device boards |
SP |  | System communication Processor, administers the sending of messages (signalling) between RP and CP. SP administers and monitors the communication bus (SC-bus) and assigns the signalling capacity between the different regional processors |
SC-bus | System Communication bus, three lines in the back plane, used for the signalling between CP and RP |
Serial communication, 64 kbit/second, half duplex |
Individual messages from CP to RP with a handshaking protocol |
Global messages (broadcast) from CP to all RPs |
Messages from RP to CP after request from RP (SP scans all RPs) |
Cards 00-63 |  | The number of the board position is permanently encoded in the printed wiring on the back plane board. These numbers are used for the addressing of signals (messages) between CP and RP. On each board a maximum of 128 individuals (individual devices) can be addressed |
LED | Light Emitting Diodes that are controlled by the regional software |
YELLOW, is used to indicate system start and (if any) blocked devices. Flash = system start. Steady glow = one or more devices on the board is/are blocked |
GREEN, is used to show whether any of the devices on the board is in traffic. Extinguished = all devices on the board are free. |

### Control of back plane connection

The connection of the device boards to the back plane is controlled from the central processor (CP) via the "Function Control Bus" (FC-bus).

The control interface uses hardware functions only on the device boards and is thus completely independent of functioning regional device processors (RP).

Functions that can be controlled from CP:

- Testing to verify whether a board is plugged in
- Connection of the board to the SC- and PCM busses
- Disconnection of the board from the SC- and PCM busses
- Resetting of the board's processors and (possibly) other circuits
- Testing to ascertain whether the board is connected/disconnected to/ from the busses

The red LED is connected directly to those circuits that connect the board to the busses and shines with a steady glow if the board is disconnected.

The processors on the device boards normally are locally monitored (watchdog) restarting the regional processor on certain fault conditions. This function results in disconnection of the individual board from the busses and the red LED lights.

In the first program editions of the PBX not all of these possibilities were utilised. At present when a fault in a regional processor is identified by the CP the PBX initiates a restart within some minutes by itself.

### Switches and transmission

Central and distributed switch system

Voice connection between two devices (telephones) is established with the help of a central switch and local switches on the device boards. These switches are connected via two bothway PCM-busses.

The Integrated Cordless has a separate PCM-bus system with 60 time slots linking the control unit and the line unit boards.

Each PCM-bus has 64 time slots (4 Mbit/second). These 128 possibilities of interconnecting different devices are administered as a central resource and are "lent" to those devices that are to be interconnected just then. The device boards will be ordered by CPU to connect an individual device if required, whereafter CP interconnects two or more devices (conference, intrusion) in the central switch.

Thus, for normal telephony two time slots are required for a connection, one for A-party and one for B-party.

128 time slots (in theory) support 64 concurrent calls. Certain time slots are used for other purposes, e.g. supplying audible tones, so approximately 60 concurrent calls are possible.

Cordless uses data compression when sending voice data to the portables so that the SPU part on the IC-LU converts the ADPCM voice data to standard PCM data and back, depending on the direction.

Some of the device boards have a local switch for rate adaptation to the PCM bus in the back plane.

On all analogue device boards transmission levels to/from the connected devices can be adapted by program-controlled functions.

MUSAC |  | Multipoint Switching and Conferencing Unit crossconnects up to 512 incoming to 256 outgoing PCM channels and connects up to 64 conference channels |
MPU |  | Conference unit (Multi Party Unit), is included in the MUSAC |
TSU |  | Tone Sender Unit, is used to generate traffic tones (ring control tone, busy tone, etc.) and DTMF-tones for digit transmission to the public telephone exchanges and other equipment |
Modem |  | Built-in modem (for remotely connected operation & maintenance) |
DSLAC |  | Digital/analogue PCM-encoder/decoder (stand. 8 bit PCM) has an integrated "switch"allowing it to be connected to any of the 2 x 64 time slots |
Adaption |  | Analogue adaption (adaptation) of transmission levels (program-controlled) or selectable by RASC |
ASIC |  | Application specific integrated circuit emulating the MC 6809 processor |
ATIA |  | Continuous adaptation of the hybrid balancing circuit on analog trunk boards featuring increased side tone stability and echo performance. Not to be used on data connection lines. |
CP |  | MC68302 control processor on the Integrated Cordless CU board. |
DASL |  | Line interface for digital telephones types DBC 6xx, DBC 2xx, DBC199 (8-bit standard PCM) |
DPRAM |  | Dual port RAM |
DIEC |  | Digital/analogue PCM-encoder/decoder for telephones type DBC 75x (6-bit PCM) |
DEC |  | Line interface for digital telephones type DBC 75x, (6-bit PCM) |
2B+D |  | ISDN connection to a digital network in the 2x64 kbits + 16 kbits format |
30B+D |  | Connection of digital trunk line, thirty connections (30B+D), with the network exchange |
EPIC |  | Extended PCM Interface Controller |
RSU |  | Register signalling unit (MFE, MFC or DTMF-receiver) |
SPU |  | Signal processing unit for conversion of ADPCM to standard PCM |
CLU |  | Communication line unit is the interface to the base stations |

Revision: K © Ericsson Enterprise 2003