MC34118-D28-T UTC [Unisonic Technologies], MC34118-D28-T Datasheet - Page 10

• Manufacturer Part Number: MC34118-D28-T
• Description: VOICE SWITCHED SPEAKER-PHONE CIRCUIT
• Manufacturer: UTC [Unisonic Technologies]

MC34118
Definition of the above is as follows:
Transmit
Receive
Fast Idle
Slow Idle
A summary of the truth table is:
1. Under all the below situations the circuit will switch to transmit :
2. Under all the below situations the circuit will switch to receive
3. Under all the below situations the circuit will switch to the fast Idle mode:
4. Under any of the below situations the circuit will switch to the slow idle mode
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*
*
Trems
(1) Both transmit level detectors sense signals relative to the respective receive level detectors
(2) The transmit background noise monitor indicates the presence of speech.
(1) Both receive level detectors sense higher signal levels relative to the respective transmit level detectors
(2) The receive background noise monitor indicates the presence of speech.
(1) If the level detectors disagree on the relative strengths of the signal levels
(2) At least one of the background noise monitor indicates speech.
There are two conditions which can cause the fast idle mode to occur:
(A) When both talkers are attempting to gain control of the system by talking at the same time
(B) When one talker is in a very noisy environment, forcing the other to continually over-ride that noise level. In
(1) Both talkers are quiet( no speech present)
(2) When one talker’s speech level is continuously over-ride by noise at the other speaker’s location.
I1 is turned on; I2 is off,
Charging the external capacitor to +240mV above VB
An internal clamp prevents further charging of the capacitor).
I2 is turned on; I1 is off,
Bringing down the voltage on the capacitor to -240mV with respect VB.
RT =120kΩ (typ.), and CT =5µF (typ.).
Switching to the receive mode
Switching to the transmit mode
FUNCTIONAL DESCRIPTION(Cont.)
TLI1 versus RLI1, TLI2 versus RLI2
general, the fast idle mode will occur infrequently.
CT pin (pin14) determine the time required to switch the circuit between transmit, receive, fast idle, and slow
idle.
A schematic of the CT circuitry operates as follows:
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The transmit attenuator is fully on: +6dB. And the receive attenuator is at max. attenuation :-46dB
Both attenuators are controlled by the volume control. At max. Volume the receive attenuator is fully
on: +6dB, and the transmit attenuator is at max.attenuation:-46dB.
Both transmit and receive speech are present in approximately equal levels.
The attenuators are quickly switched to idle until one speech level dominates the other.
Speech has ceased in both transmit and receive paths. The attenuators are then slowly switched to
the idle mode.
Definition
LINEAR INTEGRATED CIRCUIT
QW-R108-007,D
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