Tell-A-Bell
This accessory connects to phone and will activate an attention-getting 120-V bell whenever a ringing voltage appears on the ph...
Telephone Auto Record
The circuit requires neither a battery nor an ac supply to make it work. Set the recorder to the record position and ...
Telephone Silencer
If you are busy and cannot answer or do not wish to answer your phone, this circuit will give a busy signal without you ...
Low-Power Touch-Tone Decoder
This decoder will respond to a preselected 4-digit DTMF number. IC7 is a Radio Shack IC device (part #276-1303...
Telemonitor For Recording Phone Calls
This circuit switches a tape recorder via PL2. When on-hook, D5 conducts, turns on Ql, and cuts off Q...
Telephone Toll Totalizer
The Telephone Totalizer built around two 4 518 dual synchronous up counters, a 74C925 4-digit counter, a 4 58...
Telephone-Operated Ac Power Switch
Tones (from the DTMF) on the telephone line are detected by Ul. When a valid tone is received, pin 14 (D...
Dialed-phone-number-vocalizer
By vocalizing the numbers and symbols of its~eypad, the phone provides an audible confirmation that is useful to the blind. The serial-interface, 2 K-byte x 8-...
Chroma-demodulator-with-rgb-matrix
The MC1324 provides chroma demodulation recovering recooling the R, G, and B signals to drive video amps for each color difference signal. ...
Telephone-tap
Amplify or record a telephone call with the simple circuit shown. The 8-0 secondary winding of a miniature transistor output transformer is connected in series...
Wireless-telephone-eavesdropper
The IR transmitter connects to a telephone cir cuit, and transmits both sides of all telephone conversations to any line-of"sight location, within 40 feet. No...
Ring-detector
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...
Cassette-interface
Q1 and Q2 are used to form the basis of an interface circuit for attaching a cassette recorder to the phone line. The circuit does not require a power supply b...
Line-activated-solid-state-switch
Each and every time a phone on the same line or calling numberis taken off-hook, the circuit will be activated to control an external electronic circuit. If se...
Phone-recorder
This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorder"s switch terminals are ap...
Duplex-line-amplifier
This circuit is a bidirectional amplifier that can amplify both signals of a duplex telephone conversation. It uses the principle of negative resistance. Obvio...
Telephone-speech-activity-detector
This circuit can be used in telephone lines for speech activity detection purposes. This detection is very useful in the case of half-duplex conversation betwe...
Remote-telephone-ringer
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. Fin...
Telephone-sound-level-meter-monitor
The telephone-line decibel meter and line-voltage sensor shown lets you accurately monitor and adjust telephone sound levels. The 600-0 resistor properly termi...
Dial-pulse-indicator
This indicator senses the switching on and off of the 48-V de line voltage and transmits the pulses to logic circuitry. An Hl1A10 threshold coupler, with capac...