Showing posts with label telephone. Show all posts
Showing posts with label telephone. Show all posts
Saturday, October 4, 2014
Telephone line monitor Circuit Diagram
This chic little circuit lets you almanac your buzz conversations automatically. The accessory connects to the buzz line, your band recorders microphone input, and the recorders alien ascendancy jack. It senses the voltage in the buzz band and begins recording back the band drops to 5 volts or less.
Parts
R1 270K 1/4 W Resistor
R2 1.5K 1/4 W Resistor
R3 68K 1/4 W Resistor
R4 33K 1/4 W Resistor
C1 0.22uF 150 Volt Capacitor
Q1, Q2 2N4954 NPN Transistor
D1 1N645 Diode
MISC Wire, Plugs To Match Jacks On Recorder, Board, Phone Plug
Parts
R1 270K 1/4 W Resistor
R2 1.5K 1/4 W Resistor
R3 68K 1/4 W Resistor
R4 33K 1/4 W Resistor
C1 0.22uF 150 Volt Capacitor
Q1, Q2 2N4954 NPN Transistor
D1 1N645 Diode
MISC Wire, Plugs To Match Jacks On Recorder, Board, Phone Plug
Notes
1. The circuit can be placed anywhere on the phone line, even inside a phone.
2. Some countries or states require you to notify anyone you are talking to that the conversation is being recorded. Most recoders do this with a beep-beep. Also, you may have to get permission from the phone company before you connect anything to their lines.
Thursday, September 11, 2014
Contactless telephone ringer circuit
The contact less telephone ringer schema can produce a ring as well as a visual indication when a call comes.The main advantage is that since there is no direct contact between the phone line and the schema there is no chance for a loading or disturbance in the telephone line.
When the telephone rings 60 Hz AC signal is generated which produces a proportional magnetic field around the telephone lines.These magnetic field will be picked up by the coil L1 due to electromagnetic induction.A proportional voltage is developed across L1 and it will bias transistor Q1 to ON.This results in the conduction of transistors Q2,Q3 andQ4.The buzzer will ring and the LED will glow.The switch S1 acts as an ON/OFF switch.
Notes.
* For L1 make 50 close turns of 28 SWG enameled copper wire on any of the two telephone wires.Connect one end of the coil to base of Q1 and leave other end free.
* If the schema not works by try by changing the end of the L1 connected to base of Q1.
* A 9V transistor radio battery can be used as the power source.
* Assemble the schema on a good quality PCB or common board.
* Use of this type or any other devices other than the allowed telephones and devices with the telephone line may be a law violation in some nations.Check it properly before trying.
Thursday, August 14, 2014
Telephone Tapping Indicator
This simple schema can indicate a misuse or tapping of Telephone line through a loud alarm. The schema is too simple and can be easily assembled on a common PCB. Line voltage of Telephone lines is around 48 volts DC in the On hook state. When the handset is lifted, this voltage reduces to 12 volt DC. This change in voltage level is used to activate the schema.When the switch S1 is closed, schema becomes active and the telephone enters into the armed state.
Telephone Tapping Indicator Circuit diagram
Setting
Connect the schema to Telephone lines using a telephone plug. The free socket of the telephone or Caller ID can be used. Close S1 and adjust VR1 till buzzer stops beeping. Lift the handset. Buzzer should sound. Otherwise, just adjust VR1 till buzzer beeps.
Telephone Tapping Indicator Circuit diagram
The high volt DC from the telephone line passes through R1 and VR1 and bias T1 into conduction. As a result, the collector of T1 goes to ground potential to inhibit T2 from conduction. Buzzer and LED thus remain off. When the handset is lifted, the DC voltage from the telephone lines drops to 12 volts. This turns off T1 and T2 conducts. Buzzer beeps and LED lights indicating that the telephone is using.
Connect the schema to Telephone lines using a telephone plug. The free socket of the telephone or Caller ID can be used. Close S1 and adjust VR1 till buzzer stops beeping. Lift the handset. Buzzer should sound. Otherwise, just adjust VR1 till buzzer beeps.
Tuesday, August 12, 2014
Telephone Spy unit circuit
This is telephone spy unite.You can transmit signals up to 200feet.This schema operates with 88-94MHz.This schema doesnt want extra power it uses the power of the line.
Note
# If the LED burning out as a problem of your schema, add a 300 ohm 1/4W resistor in series with it
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