Radiotelephone from the radio station. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Radiotelephone from the radio station. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Telephony

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Installing a radio station in a car has become commonplace for many motorists. The proposed scheme allows using radio stations like "ONWA", "ALAN" not only for its intended purpose, but also as a radio telephone, i.e., it becomes possible to access a city PBX through a home telephone.

To do this, you need to purchase a second radio station and assemble the proposed circuit (Fig. 1).

(click to enlarge)

Let's consider the operation of the circuit in interaction with the radio station and the telephone network. In the standby mode, the stationary radio station is in the receive mode. When a call signal is received from the telephone line, the ringing voltage through the resistor R1 is applied to the input of the electronic auto-lift relay, which operates and opens the transistor VT1, which imitates the pick-up of the handset. In the future, the auto-lift mode is supported by conversational voltage. Also, when auto-raising, the transistor VT2 opens, and power is supplied to the multivibrator on the DD1 chip, which starts switching the "reception-transmission" mode of the stationary radio station with an interval of 20 s. When the radio is in the receive mode, the multivibrator is blocked by the conversational voltage, and it maintains the receive mode until the end of the conversation from the car radio. Further, the radio station is transferred to the transmission mode by the multivibrator. To simplify the circuit, this time is determined only by the parameters of the multivibrator. After 20 seconds, the radio switches back to the receive mode.

To dial a number from the car radio, a standard beeper is used, which is brought to the microphone when dialing. You can use the tone-pulse dialing method, but in this case, you must install a dialer in the car, and a selective electronic relay in the fixed station. The auto-raise relay is a standby multivibrator, the circuit of which is shown in Figure 2.

Radiotelephone from a radio station

Literature

1 Martynyuk N Miniature radiotelephone - Radio amateur, 1997, No. 11, C 17
2 Martynyuk N Radiotelephone from the receiver - Radio amateur, 1996, No. 5, C 16
3 Kotov V Telephone interface - Radio amateur, 1997, No. 2, C 18

Author: N.Martyn, Kobrin, Brest region; Publication: N. Bolshakov, rf.atnn.ru

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