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4 . CIRCUIT DESCRIPTIONS OF BASESET LOGIC
4 - 1 I N T R O D U C T I O N
The BASE LOGIC B °Ø d controls the RF PART, the TX/RX AUDIO process, the telephone line interface
and the charging circuit.
4 - 2 DESCRIPTION
a ) TELEPHONE LINE INTERFACE
The telephone line interface separates DC and AC components on the telephone line.
The DC components are used for the SPEECH IC OPERATION and the AC COMPONENTS which mean
an AUDIO signal passes to the AUDIO PROCESS CIRCUIT that the two TEL-LINES are connected
to the HOOK RELAY.
This HOOK RELAY is operated by the MPU and a switching TR.
The audio signal flows into the BRIDGE DIODE which confirms receiving the constant polarity even
though the DC polarity of TEL-LINE is reversed. This line flows into the switching circuit normally
and the switching TRs(Q5 0 3, Q5 0 4, and Q5 0 5) are switched to make pulses and Q5 0 6 is used for
matching the DC impedance during pulse dialing. The tel-line passes to the SPEECH
I C ( T E A1 1 1 8AT) which separate the DC and the AC components.
The IC passes the AC component(which means the audio signal) to audio process circuit and carries
over the TX audio signal passed from audio process circuit. The DTMF signal which is generated by MPU
itself send to SPEECH IC through TX audio path. The ring signal coupled with the C 5 0 5 goes to the
U5 0 1(PHOTO COUPLER) and goes to the MPU with the form of the rectangular wave.
b ) POWER SUPPLY CIRCUIT
The power supplied from the 9V ADAPTOR is divided into 3 parts.
The one regulated to 5V by the U5 0 4( K A7 8 0 5) is supplied to the RF B °Ø d , another regulated to 5V by the
U5 0 3( K A7 8 0 5) is supplied to the LOGIC PART and the third 9V is supplied to the charging circuit, Relay and
SPK AMP.
c ) RING DETECTOR
When it receives the ring signal from the telephone line, the ring detector(U 4:PHOTO COUPLER)
generates the pulse signal according to frequency of ringing signal. At this moment, MPU receives
the pulse signal and generates the ringing signal to Buzzer.
d ) TX/RX AUDIO CIRCUIT
The RX audio signal from the TEL LINE goes to the MPU (pin 3 7)through the SPEECH IC.
The MPU converts this audio signal into digital by internal DSP.
These digital voice signals are transmitted to RMT SET by BASE RF.
The TX digital signal from the RMT RF inputs the BASE RF module and then the digital siginal is
converted into analog audio by the MPU.
Those audio signals go to the TEL LINE through the SPEECH IC
e ) INDICATION CIRCUIT
This circuit consists of LEDS to display the baseset operation.
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Samsung Electronics
Schematic Description and Diagrams
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