Telephone-handset-encoder
This encoder uses a single contact per key keyboard and provides all other switching functions electronically. The diode connected between terminals 8 and 15 p...
Add-on-telephone-hold-button
A sensitive-gate SCR provides a line-holding current of 20 to 40 mA, depending on loop resistance. It also lights an LED to give the user a positive indication...
Parallel-telephone-connection
When the handset is lifted and power is applied to the circuit, Q2 is fed base current through R2, which in turn drives Ql. C2 is charged via R3 in series with...
Pulse-dialing-telephone
The TP5700 or TP5710 can reduce the number of components required to build a pulse-dialing telephone, as shown. The usual current source can be eliminated by u...
Series-telephone-connection
Here is a simple method of series connection into the telephone set suitable for PABX or short line applications. When the telephone handset is lifted, Cl is c...
Tone-dialing-telephone
This circuit shows the TP5700 directly interfacing to a low-voltage DTMF generator. VREGt supplies the necessary 2-V minimum bias to enable the TP5380 to sense...
Ringer-relay
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...
Hands-free-telephone
Transistor Ql of the headset amplifier circuit amplifies the 30 mV signal, that would have gone to the earphones, to .5 V. which sufficiently drives the stereo...
Single-chip-pulse-tone-dialer
The XR-T5990 single-chip pulse/tone Dialer is a silicon gate CMOS circuit which performs both pulse and tone functions. It is designed to operate directly from...
Line-current-detector
Detection of line-current flow and indicating the flow to an electrically remote point is required in line status monitoring at a variety of points in theJelep...
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 f...
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 ma...
Autopatch telephone line interface
This circuit provides for the receiver-to-phone line and phone line-to-transmitter link...
Phone auto answer and ring indicator
Ring detect circuit for automatic phone answering or tone generation...
Low line loading ring detector
Low line current loading is provided by the H11BX522 photodarlington op-tocoupler...
Telephone handset tone dial encoder
This encoder uses a single contact per key keyboard and provides all other switching function electronically. The diode between terminals 8 and 15 prevents the ...
Telephone off-hook indicator
The LED flickers when the phone is ringing or being dialed...
Telephone-line powered repertory dialer
Repertory dialer phone has a library of phone numbers to be keyed in and dialed out fifteen frequently used numbers...
Telephone-controlled tape starter
This circuit converts a tape recorder into a completely automatic telephone conversation recording instrument that needs no external power source. Voltage at th...
Telephone relay
Connected across the bell circuit of phone, this circuit closes a relay when the phone is ringing...