1.4.3.3
Station Block Diagram (Figure
FIGURE 11 STATION BLOCK DIAGRAM
Telephone Network,
transmission circuit and Handset are connected to the M.E. audio path by
the A-pair.
The B-pair is used to transmit status information between the M.E. and the station and supply
power. Microphone signals for handsfree
are phantomed between the A and B pairs.
Data Receive Transmit
converts transmitted data into logic levels for the CPU.
Power Regulator
takes power from the B-pair to supply the station circuits.
CPU Control
supervises all operations at the station, informs the main equipment of station
status and displays the status of system parameters, at the station.
Intercom Network
contains the amplifiers for the station Speaker and Microphone and a solid
state switch which the CPU operates to cut-off the microphone.
Off Hook Signalling Module
generates ring signaling under the control of the CPU.
Status Lamps
show the status of system facilities and are controlled by the CPU.
Station Keys
are used to envoke system facilities and the CPU constantly monitors their status.
Dial Pad
is used to input
digits. During normal operation the operation of the dial is
monitored by the CPU and the information is conveyed to the main equipment. Under powerfail
conditions the dial pad operates the Powerfail Dial which outputs either decadic pulses or
DTMF tones onto the A-pair for signalling on the exchange line connected to that station.
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ISSUE 1