Circuit Diagram

TRANSDUCER_AMPLIFIER

Published:2009/6/24 3:31:00 Author:May

This circuit is high-input-impedance acamplifier for a piezoelectric transducer. Input resistance is 880 M, and again of 10 isobtained.   (View)

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DISC_TAPE_PHASE_MODULATED_READBACK_SYSTEMS

Published:2009/6/24 3:44:00 Author:Jessie

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AM_RADIO

Published:2009/6/24 3:31:00 Author:May

A IS4 regenerative detector feeds an LM386 audio IC (IC1). 1.5-V D cells and three 9-V batteries are used for a power supply.   (View)

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TELEPHONE_LINE_TESTER

Published:2009/6/24 3:30:00 Author:May

The telephone-line tester shown in the figure is connected to the telephone line through modular connector P1. Because the tester's LED polarity indicator is always connected when the tester is plugged in, the instant that the unit is connected, you will have an indication of the polarity. If it is correct-that is, if the green wire is the positive side and the red wire is the negative side-nothing will happen. If the situation is reversed, the LED will light.With switch S1 set for LINE/RING, both S1-a and S1-b are open and the meter indicates the con-dition of the line voltage. Any line-voltage reading in the LINE Ok range (more on the meter in a rno-ment) indicates a tine voltage that is higher than 40 Vdc. If the telephone is caused to ring, either by using a ringback number or by dialing from another phone, the meter will indicate RING Ok, and the LED will pulse (indicating ac), if the ringing voltage/current is correct. The actual position of the me-ter's pointer depends on how many ringers are connected across the line.When S1 is closed the voltage range of the meter is changed and a nominal load resistance of 230 Ω (R5 and R6) is connected across the line to emulate the off-hook load of the telephone. If the meter indicates LOOP Ok, you can be certain that you have sufficient loop voltage for satisfactory telephone operation. If you place another load on the line, perhaps by taking an extension telephone off hook, the meter reading will almost invariably drop below the LOOP Ok range. If lifting the hand-set causes the meter reading to drop;you can at least be certain that the telephone's hook switch is working and that the repeat coil is connected to the line.   (View)

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PHONE_HELPER

Published:2009/6/24 3:44:00 Author:Jessie

This phone-line simulator uses a 60-Hz transformer instead of a ring generator. The dial tone is provided by an NE555 astable oscillator.   (View)

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ELECTRONIC_BALANCED_INPUT_MICROPHONE_AMPLIFIER

Published:2009/6/24 3:30:00 Author:May

It is possible to simulate the balanced per-formance of a transformer electronically with a different amplifier. By adjusting the presets, the resistor ratio can be balanced so that the best CMRR is obtained. It is possible to get a better CMRR than from a transformer. Use a RC4136 which is a quad low noise op amp.   (View)

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BASIC_TRANSISTOR_AMPLIFIER_CIRCUITS

Published:2009/6/24 3:29:00 Author:May

Typical component values are given for use at audio frequencies, where these circuits are used most often. The input and output phase relationships are shown.   (View)

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ION_DETECTOR

Published:2009/6/24 3:28:00 Author:May

ANT1 is a short whip antenna from a junked radio or other device. R3 is adjusted to bring the meter on scale. This device should be grounded to operate properly. A length of aluminum or copper foil tape attached to the instrument case makes contact with the hand, and the body senres as a ground via hand contact with this tape.   (View)

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TRANSFORMERLESS_MICROPHONE_PREAMPS_UNBALANCED_INPUTS

Published:2009/6/24 3:40:00 Author:Jessie

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TRANSFORME_RLESS_BALANCE_INPUTS_MICROPHONE_PREAMP

Published:2009/6/24 3:39:00 Author:Jessie

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TELEPHONE_AUDIO_INTERFACE

Published:2009/6/24 3:39:00 Author:Jessie

The telephone audio interface-essentially, a simple isolation/couple circuit-isolates the phone line from any connected audio circuit without presenting any danger to the phone line, the equip-rnent, or the user.   (View)

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BISTABLE_MULTIVIBRATOR

Published:2009/6/24 3:38:00 Author:Jessie

Positive feedback is provided by resistor R4, which causes the latching. A positive pulse at the set input causes the output to go high and a reset positive pulse will return the output to es-sentially 0 Vdc.   (View)

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PHOTORECEIVER_OPTIMIZED_FOR_NOISE_AND_RESPONSE

Published:2009/6/24 3:28:00 Author:May

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ac／dc_VACUUM_TUBE_AM_AND_SHORTWAVE_RECEIVER

Published:2009/6/24 3:38:00 Author:Jessie

This circuit was used in a World War II vintage AM／SW（6 to 18 MHz）recelver and shows typical circuits used in recelvers at that time.   (View)

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SYNCHRONIZER_CIRCUIT

Published:2009/6/24 3:28:00 Author:May

This common synchronization method uses two rippled 74LS74 D-type flip-flops.   (View)

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BELL_SYSTEM_202_DATA_ENCODER

Published:2009/6/24 3:38:00 Author:Jessie

The AD537 is well-suited for frequency-shift modulator and demodulator applications. Requir-ing little power, it is especially appropriate for using phone-line power. The Bell-System 202 data en-coder shown here delivers the mark frequency of 1.2 kHz with the data input low. When the input goes high, the timing current increases to 165 μA and generates the space frequency of 2.2 kHz. The trim shown provides a ±10% range of frequency adjustment. The output goes to the required band-pass filter before transmission over a public telephone line. A complementary demodulator is easy to implement.   (View)

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GENERAL_PURPOSE_PREAMPLIFIER

Published:2009/6/24 3:28:00 Author:May

Not much can be said about how the LM382 works as most of the circuitry is contained within the IC. Most of the frequency-determining components are on the chip-only the capacitors are mounted externally. The LM382 has the convenient characteristic of rejecting ripple on the supply line by about 100 dB, thus greatly reducing the quality requirment for the power supply.   (View)

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SYNC_STRETCHER_CIRCUIT

Published:2009/6/24 3:27:00 Author:May

Q1, Q2, and Q3 comprise a simple video amplifier and sync stretch circuit. Transistor Q1 sync strips the incoming video, which is amplified and mixed with the stripped sync in Q2. Q3 supplies in-version and video amplitude control.   (View)

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TELEPHONE_SCRAMBLER

Published:2009/6/24 3:36:00 Author:Jessie

This circuit uses the usual speech inversion algorithm, implementing it with a COM9046 ASIC. This unit is designed to fit be-Lween the handset and base of a standard telephone. It is powered by a 9-V battery.   (View)

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ASTABLE_MULTIVIBRATOR_WITH_STARTING_NETWORK

Published:2009/6/24 3:35:00 Author:Jessie

This circuit will start with a slowly rising supply voltage waveform.   (View)

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