Simple audio signal injector

Here's a signal injector for those of us like me who don't have a bench full of nice test equipment. It can be used for tracing audio circuits for troubleshooting, or for working on audio circuits that require some kind of signal for testing.

The injector is a single-transistor implementation of the classic twin-T oscillator circuit. I actually found this in the ARRL (Amateur Radio Radio League) Handbook, and adapted it for my purposes. The transistor type is absolutely non-critical: any small-signal NPN transistor will do. Likewise, component values aren't crucial, and you can change them for different frequency output if you like. (As built, the injector gives about a 1 kHz tone at about 1v p/p.)

The whole thing can be built on a tiny scrap of perfboard and mounted in a small box (I used an Altoids-type metal lozenge box).

RANGKAIAN AUDIO LEVEL (with LED)

Untuk menyatakan level audio biasanya digunakan VU (voltmeter unit) yang akan menunjukkan secara visual naik turunnya suara output dari sebuah perangkat audio (tape, radio, MP3 dsb). pada project ini untuk menggantikan VU digunakan deretan LED yang nyalanya kan mewakili secara visual suara output. Bagian ini hanya bentuk mono untuk menjadikan stereo maka harus membuat rangkaian yang serupa.

Karakteristik:
sensitivitas sampai 1 volt, +6dB. Untuk mengubah amplitudo input dapat dilakukan dengan mengatur multitun 50 K (POT1). Delay visual dapat di atur oleh 10K potensio (POT2). Sebagai pengatur nyala LED digunakan LM3915 (display driver for LED, LCD etc).

Layout:
Schematic:

Simple Telephone Central Project

This simple telephone switching system is designed by Dr. Mustafa Kemal PEKER
for training purposes. All responsibility is belong to user. Schematic and code is
under GNU public licence. Cannot be used as commercially. If you interested in
with two or more subscriber models with DTMF, please contact to author.
mkpeker@yahoo.com

WORK

1) System contains 1 subscriber and 1 central
2) Central cannot call.
3) When subscriber hangs up, Central rings.
4) When central answers, ringing stops.
5) Conversation ends when one side closes the phone.

For simplicity you may use an old AT computer power supply which includes
12v and 5v. Have fun.....

Attached Files

• santral.HEX (2.4 KB, 186 views)

20 Watt Power Amplifier

This IC chip was designed specifically for use in power boosting applications in automobiles. It is self protecting against short circuits and thermal problems. In the bridge configuration shown it will deliver 20 watts of power into a 2 ohm speaker operating at 14.4 volts.

Attached Files

• Santral.GIF (9.2 KB, 285 views)
• santral.HEX (2.4 KB, 177 views)