|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Telephone interface for SI-BI radio station. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Telephony Telephone interfaces are used to connect a CB radio station to a telephone line. The proposed article introduces a simple version of such a device. It should be borne in mind that non-certified devices cannot be connected to the public telephone network. The interface can only be used on departmental and office PBXs. The need to develop a telephone interface arose due to the lack of simple and cheap devices on the market for connecting 27 MHz radio stations to a telephone line. Devices manufactured by foreign companies, such as the SC-900 and LMR-2 types, are expensive. True, they provide communication between the radio subscriber and the subscriber of the telephone network in automatic mode. Similar Russian-made devices are cheaper, but their quality leaves much to be desired. In addition, in conditions of strong interference, the operation of any interface is possible only in manual mode, i.e. the dispatcher dials the number and connects the radio subscriber to the telephone line. In this regard, a manual interface was developed. The interface is made in three versions, it was connected to stations of different types, showing reliability in operation and high quality of communication. The design of the interface turned out to be technologically advanced, easy to repeat and non-critical to the types of parts used. Extensive customization options allow you to connect the interface to almost any radio station with minimal changes. With careful tuning, the quality of communication is not worse than that of interfaces of the SC-900 and LMR-2 types. The interface is connected to the radio station through the microphone connector without changes in the design of the station itself. It provides two-way simplex communication between a radio subscriber and a subscriber of a city or long-distance telephone network, as well as communication between a dispatcher and a radio subscriber. All standard functions of the radio station are fully preserved. The number is dialed by the dispatcher from a separate phone (if the interface is made as a separate structure) or directly from the interface phone (if the interface is built into the phone).
The diagram of the device is shown in the figure. Here is the decoding of some designations of the pins of the connector to which the microphone of the radio station is connected:
The basis of the device is signal detectors A1 and A2. Detector A1 receives a signal from a radio station, and A2 - from a telephone line. The circuitry of these blocks is similar, they differ only in that A2 has an additional signal amplifier on the transistor VT3. Consider the operation of one of the blocks, for example A2. The signal passes through the capacitor C6 to the transistor VT3, is amplified by it and fed to the rectifier with voltage doubling (VD4, VD5). The composite transistor VT4VT5 opens and relay K2 is activated, which performs the necessary switching. Parallel to the relay, the HL3 LED is turned on, which serves as an indicator of the relay operation. Switch SA1 is used to select the operating mode. In the pressed position, the "Interface" mode is enabled, and in the pressed position, the radio station and the telephone perform their main functions. If a signal comes from the line, then relay K2 is activated. It disconnects A2.1 from the radio station with its contacts K1 (to prevent false operation of K1), contacts K2.2 closes the PTT output to a common wire, which leads to switching the radio station to transmission mode, and contacts K2.3 connects the microphone input of the radio station to an isolation transformer T1 (i.e., to the telephone line). Contacts K2.4 disconnect A1 from the power source and provide recharging of the capacitor C2 for a clearer operation of the relay K1. If a signal comes from the radio station (the SPK output is used, which has a low frequency voltage), the K1 relay is activated, it connects the SPK output to the T1.1 transformer with its contacts K 1, and the signal from the radio station enters the telephone line. Contacts K1.2 disconnect block A2 from the line to prevent false operation of relay K2. The interface can be made in the form of a separate design or built into the telephone with both push-button and mechanical dialer. The first option is to embed the interface into a phone with any dialer. Contacts SA1.7, when operating in interface mode, connect the phone through a resistor R12, which is necessary to reduce the shunting effect of the conversational part of the phone on the operation of the interface and enable the dispatcher to listen to conversations through the interface. SA1.8 pins turn off the microphone of the handset, which increases the stability of the interface. In this option (it is shown in the diagram) it is not possible to dial a number in the "Interface" mode. Option two - embedding the interface into a telephone with a rotary dialer. In this case, you can dial the number in the "Interface" mode. To implement this option, it is necessary to connect the conclusions shown in the diagram "To the telephone set" to the conversational node of the telephone, and the conclusions "To the telephone line" - to the telephone after the dialer. The device is connected to the line in the usual way. The third option is to connect an interface made in the form of a separate set-top box. It differs from the first option in that the SA1.8 contacts are not used, the microphone is not turned off, so self-excitation may occur. Transistors VT1-VT5 can be any of the KT315, KT312, KT3102 series. Relay K1 - RES-22, passport RF4500163, K2 -RES-9, passport RS4524202. Switch SA1 - P2K or any with eight switching contacts. Transformer T1 - any small-sized transitional transformer from a transistor radio. The primary winding should be with less resistance, and the secondary with more. The resistance of the primary winding is within tens of ohms, and the secondary - hundreds of ohms. It is possible to use a 1:1 transformer, but in any case, the resistance of the primary winding must be at least 50 ohms. A properly installed device starts working immediately and does not need to be configured, but due to differences in radio stations, it may still be required. There are five points where the circuit must be broken in order to ensure normal operation. These points are marked on the diagram A - E. The circuit at point B must be broken in case of self-excitation of the ULF radio station in the "Interface" mode. At point G, break the circuit in case of self-excitation in transmission mode (for example, for YOSAN-2204 or another radio station with a condenser microphone). If the relay K1 is indistinctly actuated, it is necessary to break the circuit at point D. If the microphone is not electret and you do not need to supply power to it, you need to break the circuit at point B. Resistor R6 is selected according to the optimal signal level at the microphone input of the radio station within 1,5 ... 10 kOhm, depending on the type of radio station. The resistance of the resistor R6 should not be less than 1,5 kOhm in order to avoid failure of the radio circuits. By selecting time-setting capacitors C2 and C8 in the range from 2 to 20 microfarads, it is necessary to achieve reliable operation of the relay, as well as to select the optimal time for its release. It is advisable to use foreign-made capacitors, since Russian ones do not provide the required capacitance stability. The variable resistor R7 sets the threshold for the signal from the telephone line. It makes sense to bring this resistor to the front panel, since the signal level from the PBX can change arbitrarily and, therefore, it will be necessary to adjust the threshold for the K2 relay. If there is no power output (13.8 V) on the radio station connector, you need to apply this voltage there (MegaJet-2701 type connector) or connect the interface to the power supply with separate wires. It happens that the interface does not work correctly when connected to the SPK contact. Then, instead of an output, the SPK is connected directly to the built-in dynamic head of the radio station. To do this, break the circuit at point A and connect the dynamic head to the connection point of contacts K1.1 and K2.1. In this case, the circuit is also broken at point B. It may be necessary to select a transformer T1 if the signal level from the telephone line is not enough. The connection of the interface to the radio and the PTT to the interface must be made with a shielded five-wire cable. If using an unshielded cable, it may be necessary to disconnect the microphone circuit from the PTT (due to interference) in receive mode. To do this, you can use a separate small-sized relay with a response voltage of 12 V (RES-15, etc.), by connecting the winding to the power output and to the PTT contact, of course, after the SA1.1 switch. Author: S.Lushnikov, Blagoveshchensk, Amur Region; Publication: N. Bolshakov, rf.atnn.ru
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ Moto G Google Play Edition smartphone with Android 4.4 KitKat ▪ Bioelectric stimulation in medicine ▪ Soluble plastic from mango and algae
▪ section of the website job descriptions. Article selection ▪ article Look back in anger. Popular expression ▪ article From what distance can a salmon catch the smell of its native river? Detailed answer ▪ article Glass cleaner. Job description ▪ article Turning the vest inside out. Focus Secret
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page