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When the telephone rings. or when the handset is lifted, ~the night light is turned on and remains on while the conversation takes place. When the handset is replaced in the cradle, the light remains on for about 11 s. During standby conditions, the -28 V de bias on the phone line maintains the output of U3 in a high state. When the ac ring signal is applied to the phone line, it is...
Programmable multi-tone telephone ringer
Two BST72 transistors provide an output voltage swing almost equal to the voltage at C3.
Telephone Visual Ring Indicator
In this circuit, the ringing voltage on a telephone line causes NE-1 to break over, triggering SCR1, which
Low line loading ring detector
Low line current loading is provided by the H11BX522 photodarlington op-tocoupler
Telephone ringer piezoelectric
The electronic bell needs no power supply. Most of the resistors are not critical, although C2, R2, and R3 work best at the values given. Leaving out Rl will make the unit ring louder. The piezo buzzer may vary from store to store. If it has two leads, connect the red lead to the collector and the black lead to the emitter of Ql
Simple Ring Detector
This circuit detects the 20-Hz approximately 86-Vrms ring signal on telephone lines and initiates action in an electri
This ring detector, utilizing a neon-LDR (light dependent resistor) optocoupler, simplifies inter
Circuit monitors blinking phone lights
A 2N5777 photo-Darlington cell picks up blinking light from the transparent plastic buttons. The power is switched ON and OFF by a hi-beta 2N3904 transistor. The circuit's 9 V battery can be left continuously connected. Less than a micro-ampere is drawn-even with normal, office ambient light and the phone lights not flashing.
Remote ring extender switch
The circuit can operate lamps and buzzers from the 120 V, 60 Hz power line while maintaining positive isolation betweenthe telephone line and the power line
Telephone Ring Converter Circuit
The circuit is based on the TCM1506 ring detector/driver integrated circuit. It is a monolithic IC specifically designed to replace-the telephone`s mechanical bell. The chip is powered and activated by the telephone-line ring, which can vary from 40 to 150 V rms at a frequency of from 15 to 68 Hz. No other source of power is required. Again, referring to the figure shown, CI through C5 are...
This circuit detects the 20 Hz, "" 86-V rms ring signal on telephone lines and initiates action in an electrically isolated circuit. Typical applications would include automatic answering equipment, and interconnect/ interface and key systems. The circuits illustrated are bare bones circuits designed to illustrate concepts. They might not eliminate the ac/dc ring differentiation, 60-Hz noise...
Musical telephone ringer
The heart of the circuit is IC1, General Instrument's AY-3-1350 melody-synthesizer IC. IC2 is a TCM1512 telephone ring detector IC that is powered by the telephone line. The circuit's operation begins when IC2 senses a ring pulse on the telephone line. The detector (internally) rectifies the ring signal and then outputs a voltage to relay RY1 (an SPST reed-type relay with 5 volt contacts),...
Electronic phone bell
The speaker emits a distinctive warble tone when ring pulses are applied to the phone line. Use this circuit as a remote bell or disconnect the phone"s ringer for direct use. Rl adjusts the duration of the output; R2 and R3 control the tone"s duty cycle and frequency. The transistor is a general-purpose NPN photodevice
When the phone rings, the ring signal from the telephone company lights a neon lamp within a CLM3120 optocoupler. That causes a drop in the resistance of the CdS cell output of the device, turning on transistor Ql.
Tone ringer II
The XR-T8205 Tone Ringer is primarily intended as a replacement for the mechanical telephone bell. The device can be.powered directly from telephone ac ringing voltage or from a separate dc supply. An adjustable trigger level is provided with an external resistor.
Telephone Bell Simulator Circuit
This circuit is intended for use in a small private telephone installation. The ringing tone sequence is 400 ms on, 200 ms off, 400 ms on, 2 ms off. In the accompanying diagram, N1 and N2 form an oscillator that operates at a frequency of 5 Hz, which gives a period of 200 ms. The oscillator signal is fed to two decade scalers, which are connected in such a manner (by N3 and N4) that the input...
High isolation telephone ringer
The diode rectifies the ringing signal to supply the operating power to the audio relaxation oscillator made up of LI, L2, Rl, R2, and C. Moreover, L2 together with Ql acts as an opto-isolator, totally isolating the telephone line from the rest of the circuit. The oscillator audio frequency is optically coupled to the photo-Darlington which drives Q2 and thus the speaker.
The MC34012 tone-ringer chip derives its power by rectifying the ac ringing signal. That signal is normally at 20 Hz and measures between 70 and 130 volts rms. It uses that power for the tone generator and to drive the piezoelectric transducer. The sound that is produced is a warble that varies between two frequencies, f0/4 (f0 - 4) f0/5. The clock, or fundamental, frequency, f0, is generated...
Call Tone Generator
Amateur VHF relay stations are normally actuated by a 1750-Hz call tone. This might give problems if the relevant sendi
Phone auto answer and ring indicator
Ring detect circuit for automatic phone answering or tone generation
The two neon bulbs will light when more than 100 V is across the ringing circuit. The bulbs provide line isolation between the unit and the telephone line. Finally, they act as a voltage divider for the bridge rectifier made up of D 1 through D4. That voltage divider creates a positive voltage that is then applied through D5, is filtered by R2, R3, and C2, and causes Q1 and Q2 to conduct.
Extension Phone Ringer
The ac ringing voltage (typically 40 to 90 V at 26 Hz) is rectified by U1, the tone-ringer IC, and is used to drive
Plug-in remote telephone ringer
This device consists of a ring detector connected to the telephone line. When the telephone rings, the ring detector impresses high-frequency pulses on the ac power line.
Telephone in-use indicator
This circuit functions as a line-current sensor and can be connected in series with either of the phone lines. For the circuit to indicate an "in use" status for all phones on a single line, it must be connected in series with the phone line before, or ahead of all phones on the line.
Telephone or extension tone ringer
This circuit uses ML8204/ML8205 devices
Telephone tone ringer
This is a complete telephone bell replacement circuit with minimum external components with on-chip diode bridge and transient protection
Telephone ringing detector
With the 555 timer connected as a multivibrator and an opto-isolator,
Telephone Ring Indicator Circuit
A neon lamp can easily be added to the phone line to act as a ring indicator.
TELEPHONE RING SIMULATOR
This project has been specially designed to introduce you to SMD (Surface Mount Devices). Surface Mount is really not new. It started as far back as 1940 with a hybrid circuit in a digital watch. A chip was cemented onto a slab of ceramic material having gold tracks and film resistors. The LED display was mounted in a similar fashion and the whole assembly coated in epoxy to protect it before...
Telephone Ring-Tone Generation
Here is a design that you can own, tailor to your specific needs, layout on your circuit board and put on your bill of materials. Finally, you will be in control of the black magic (and high voltages) of ring-tone generation.
Phone line Audio Visual Ringer
Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external...
Ringing Phone Light Flasher
I have received several emails asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device.