Install the radio in the car has become commonplace for many motorists, the proposed scheme allows the use of the radio type "ONWA", "ALAN" not only for its intended purpose, but as a radiotelephone, that is, there is a possibility of exit using the home phone on urban ATS.
You need to purchase a second radio and to collect the proposed scheme (figure 1).
Consider the circuit in cooperation with the radio and the telephone network In stationary standby mode the radio is in receive mode. When receiving a call signal from the telephone line, the ringing voltage across the resistor R1 is input to the electronic relay of auto-pick, which activates and opens the transistor VT1 than imitated by picking up the handset In a further mode supports auto-pick spoken voltage. Also, when auto-pick opens the transistor VT2, and provides power to the multivibrator on the chip DD1, which begins to switch the mode of the reception-transfer stationary radio station with an interval of 20 s. When the radio is in receive mode, conversational voltage is blocked switching of the multivibrator, and it supports the reception mode until the end of the conversation from the car radio. Further, the radio station of the multivibrator is transferred in the transfer mode. To simplify the circuit this time is determined only by the parameters of the multivibrator 20 with the radio returns to the receive mode.
To dial from the car radio is standard beeper, which is brought to the microphone when dialing. You can use tone and pulse dialing method, but in this case it is recommended that you install a dialer, and a stationary station - selective electronic relay. Relay auto-pick is a waiting multivibrator, whose scheme is shown in figure 2.
Literature
1 Martynyuk N Miniature radio - Ham, 1997, No. 11, 17
2 Martynyuk N Cordless telephone from the receiver - Ham, 1996, No. 5, 16
3 Cats In the Telephone interface - Ham, 1997, No. 2, 18
Author: N. Martyn, Kobrin, Brest region; Publication: N. Bolshakov, rf.atnn.ru