The traditional many machine communication system needs four lines to complete generally:
1. power line; 2. grounding; 3. transmits the holding wire; 4. receives the holding wire. However, is away from regarding the main engine and the extension telephone is far, divides radio station number many systems, uses the four-wire system the funds investment to be big, installs is also quite difficult. Based on this question, this article unifies for some hospital development both has the simulated signal (pronunciation) and to have the digital signal transmission ringing system, proposed that realizes many machine communications with the single main line, and has given a complete technical program.
1 single main line system many machine communication system’s main line design proposal
This design realizes the many machine ringing system’s major function is: Extension telephone call main engine, use monolithic microcomputer to main engine transmission digit call information, after main engine response, demonstrated call’s extension telephone number, turns on the main engine and extension telephone’s analog channel carries on the main engine and the extension telephone to says; The main engine calls some extension telephone, the main engine part output extension telephone number, turns on the corresponding extension telephone’s analog channel directly, carries on the extension telephone and the main engine to says; The group calling, mainly one by one transmits opens all extension telephone’s numerical information, within several seconds turn on all extension telephone’s analog channel, the main engine to various extension telephones transmission voice signal. Realizes this kind of machine communication core question with the single main line system is the power source, how the grounding and the holding wire to assign, how does clear signal’s two-way transmission, how solve between them the mutual disturbance. The author (including digital signal and simulated signal) and the power source uses in common the signal a line, another for grounding - - single main line system. In the circuit structure and the technology, uses the power source isolating circuit, the enormous limit reduces the power source filter to the signal the influence; Completes with the anti-side tone circuit to simulated signal processing. Main engine circuitry diagram as shown in Figure 1.
When the main engine needs with some machine telephone conversation, the operator takes up the microphone, through the commonly used telephone keyboard digit dialing, the monitor demonstrated extension telephone number which calls, simultaneously, transmits the digital signal the main line, the extension telephone receives when the digital signal and confirms the main engine request telephone conversation, connection analog channel. Main engine’s voice signal after power amplifier, single main line to extension telephone’s power amplifier impetus speaker. Extension telephone’s voice signal enlarges, the anti-side tone circuit, the single main line after the power amplifier to main engine’s power amplifier impetus speaker or the receiver. Over and out, the main engine hung up, at the same time, main engine’s microcomputer sent out the stop display signal and the extension telephone hangs up the signal, the monitor extinguishment, after the extension telephone receives hung up the signal, causes extension telephone’s analog channel’s place aerosol, thus has completed a telephone conversation process.
When the main engine needs simultaneously to put through with various extension telephones, for example in the hospital needs when informs some matter all hospital beds, if with the keyboard one by one dials the extension telephone, was inconceivable. This design considers this aspect the question, so long as the operator presses the group calling key, may put through various extension telephones within several seconds to realize the group calling.
When the extension telephone needs to talk over the telephone with the main engine, according to talks over the telephone the pressed key (extension telephone only this pressed key), the monolithic microcomputer sends out the digital signal, delivers main engine’s monolithic microcomputer after the single main line. After the main engine monolithic microcomputer receives the signal, demonstrates the extension number, judges the telephone whether to hang up, if to hang up the condition, then the cycle-criterion hangs up until the telephone, after taking up the microphone, the main engine sent out the permission telephone conversation immediately to the corresponding extension telephone the signal, the extension telephone connection analog channel then may carry on the telephone conversation, over and out, the microphone hangs up, the main engine will hang up the signal to the extension telephone transmission, the extension telephone analog channel’s place aerosol. Thus, both saved the electrical energy and not to interfere with the eloquent machine partial personnel’s normal work.
The communication priority, regarding the hospital serious illness number, institution’s critical department and so on, in the ringing system must the primordial consideration. In this design, after the main engine receives the numerous calling signals, first judges the priority, the connection priority highest extension telephone telephone conversation, then gradually and low priority extension telephone telephone conversation.
2 power source isolation
In the single main line system many machine communication systems, the digital signal, the simulated signal and the power source use in common a line, if does not take the measure, alternation digital signal and simulated signal by power source’s filter capacitor absorption. When this design, has not added the power source isolating circuit, alternation 5V signal after transmission line after the extension telephone only has 10mV. After using as shown in Figure 2 the isolating circuit, the signal passes to the extension telephone to be bigger than 250mV, the signal attenuation range has the distinct improvement. In the chart diode, the triode, the stabilovolt, the inductance and the resistance isolating circuit uses in the main engine, but the extension telephone only needs an inductance and a diode then.
3 simulated signal processing electric circuit
The single main line both must transmit the voice signal, and must receive the voice signal, will form the circulation inevitably. In order to solve time the speech hears own sound (to be called side sound), has taken the anti side tone measure. Generally, the anti side tone has plants the method: One kind is bridge-type disappears the side electric circuit; Another kind is the phase counter-balance method anti-side tone circuit, the latter effect is better. Considers to a main engine and many extension telephone’s cost debugging factors, therefore the main engine part uses the phase counter-balance anti-side tone circuit, the extension telephone uses the bridge-type anti-side tone circuit.
Phase counter-balance anti-side tone circuit as shown in Figure 3, this electric circuit by three operational amplifiers and the corresponding resistance, the electric capacity and the potentiometer is composed. Extension telephone signal which comes by the main line after RW1, F3 to power amplifier, a main engine’s microphone signal pass power amplifier 1, main line, RW1 to F3 synchronism input end, another one goes via F1, F2, RW2 to the F3 opposition input end. Adjusts suitable K, C, RW1, the RW2 value to be possible to cause main engine’s microphone signal to bend down in F3 out-port close zero, thus the side sound is eliminated.
Bridge-type anti-side tone circuit as shown in Figure 4. The entire electric circuit by a country transistor (pronunciation transmission enlargement) and R, the C part is composed, in the chart ZL is outside line’s equivalent impedance. When this extension telephone transmission telephone signal, outputs the monofrequent signaling current by the triode emitter electrode, country pass outwire ZL and resistance R3 adds to triode’s emitter electrode to form the current loop again; Another country Lu Zejing R1, C1, R2 and C2 form the current loop. If bridge balance, namely
ZL (R2-j1/ωC2) =R3 (R1-j1/ωC1) Vc0=0
Because, the level power amplifier’s input signal is zero, therefore the speaker does not emit sound, leans the sound to eliminate. Main engine simulated signal which comes through the main line, after carries on the voltage amplification R1, C1 and RC to the voltage amplifier to carry on the power amplification again.
