Data Transmit And Receive; Speech Circuit; Tone Generator; Audio Selector - Telstra Commander E105 Installation And Maintenance Manual

Data Transmit and
Receive

Speech Circuit

Tone Generator

Audio Selector

Audio Amplifier

line Access Circuit

HRDB-E Board (In Master
Keystation)

Line-Hold Circuit

Ring Detect Circuit

Converts data transmitted on the bus power pair into logic levels, then
directs the signal to the keystation MCU serial port signalling interface.
Provides an interface for the telephone network intercom channel,
transmission circuit and handset.
Provides the DTMF tone and all audible tones emitted by the
keystation.
This circuit couples either:
audio signals from the speech circuit to the audio amplifier when
connected to either the telephone line or the bus,
or
.
audible tones from the tone generator to the audio amplilier when
required for either audible tones in the earpiece or transmission of
DTMF signals.
Under control of the audio selector, the audio amplifier drives the
keystation speaker. Line access connects lines to the speech circuit by
an MCU-controlled relay.
Provides an interface between the speech circuit and either of the
exchange lines. It also provides a solid-state switch fordialling
purposes.
The HRDB-E board is contained in the system Master Keystation.
Provides line-holding control at the master keystation in the system.
All other keystations in the system can assert line-holding control. They
can also transmit and receive the line hold on/off codes (received by the
master keystation) along the bus communications channel (service a and
service b) .
Provides ring detection for the master keystation only. All other
keystations in the system respond to "line ringing" and "line terminated"
codes transmitted by the master keystation along the bus
communications channel.