Offer a device that allows you to connect to a telephone line an additional subscriber.
For communication method is used to redial the number, i.e. calling and hearing the whistle of call control, you need to hang up and immediately dial the number again.
In addition, the device contains additional blocks that allow to take into account the time of the conversation and to control long distance calls.
The device consists of three functionally complete units:basic and two service - unit of time talking and cluster analysis of the HSE.
Let us consider the operation of the base unit (Fig.1).
When receiving inductor call, the output of the diode bridge VD1 (point a) you receive the pulse voltage amplitude of 120 V and a frequency of 25 Hz. Pulse duration - 1C, pause - 4C. The Comparator D1.1 converts this voltage into a series of rectangular pulses of level, the MOS IC.
From the output of D1.1 pulses are fed to the single vibrators D2.1, 02.2. A Single-Shot D2.1 has a time constant equal to 5, i.e. the period of the inductor parcels. A Single-Shot D2.2 converts the pulses from the output of the comparator in a single pulse with a duration of 1 s.
In idle mode, an incoming call, both the subscriber connected to a telephone line via public keys DA1...DA4. Opens the keys to a logic level "1" coming from the output element D1.2 through the transistor VT2 and diodes VD13, VD14.
With the arrival of the first inductor parcels triggers a single-shot D2.1, whereby its output is a logic level "1", and the output inverter D1.2 is a logical "On". The "1" level through the diodes VD2, VD3 is supplied to the inputs R triggers D6.1, D6.2, resetting them to zero and thereby disconnecting both subscribers from the telephone line. At this point, it is determined to which the subscriber is primary or secondary - is addressed to the challenge.
If the call goes to main user, inductor parcel from the output of single-shot D2.2 through the delay circuit D1.3, D1.4 and a public key VT1 is supplied to the counter D4. After counting to five pulses of the self-locking counter input V. output 5 (pin 1) D4 logical "1" through the diode VD8 is input to S (pin 14) of the trigger D6.1 sets it to "1" and thereby opens the keys DA1, DA2, connecting to the telephone line of the primary subscriber. Simultaneously with the output of the inverter D3.1 the logic level "0" stops the pulse output D2.1.
When hook the primary subscriber in the telephone circuit current begins to flow. The resistor R11, the voltage drops about 8 In relation to common wire, which corresponds to the passport data of logic level "1", the MOS IC. Resistors R11, R12 do not have any influence on the operation of the phone, and its value can vary within a narrow range for the selection of the voltage at which there is a clear logic is triggered. The voltage from the resistor R11 is fed through diodes VD15, VD16 to the input S D6.1 and R D6.2. As a result primary subscriber is permanently connected to the telephone line and the secondary is disabled. In principle, the diode VD15 may be excluded from the scheme, because the input SD6.1 receives a logic level "1" output from the 5 D4. For a more reliable lock additional telephone subscriber in the scheme included the keys VT2...VT4. The key VT2 disables the inverter output D1.2 when you pick up the handset, and the key VT3 advanced "puts" on the ground resistor R12.
At the end of the conversation the primary subscriber, when he puts the handset on the telephone, the decay of the logic level "1" on the resistor R11 is triggered pulse shaper on the element D3.4. The logic level "1" from the output of the shaper counters are reset D4, D5, preparing the device for the next reception of the call. Counter D5 when the host calls the subscriber on the operation of the circuit is not affected. He needed to control the key VT1 and saving the calculation result of the first series inductor parcels when dialing up to an additional subscriber. Since the release of the single vibrator D2.1 on the entrance D5 comes one pulse when dialing to the subscriber, on the base of the transistor VT1 there is a "1" level, and the transistor is open.
The mode of the incoming call additional subscriber. Call for more subscriber selected redialing. Thus, without waiting for the arrival of the fifth ringback call, press the release lever. Just as in the first case, the shutdown of both subscribers to determine the destination of the call. Counter D4 will have time to count 2-4 pulse. After redialing the first inductor parcel switches the counter D5 in the state corresponding to two pulses counted, the key VT1 is closed, not missing pulses to the counting input D4. After 5 seconds after pressing the release lever on the inputs of the element D3.2 will present the logical levels "O" and "1". The output of this element appears a logic level "1", which triggers a single-shot D2.3, includes 1...2 min additional telephone subscriber.
To exclude a concurrent income levels logic "1" to the inputs of the flip-flop D6.2 from the outputs of the single vibrators D2.1, D2.3, the key on the transistor VT9 when you pick up the handset any subscriber "puts" exit D2.1 through a resistor R19 to the ground. If the 1...2 min, the tube was not removed, the decay of the positive pulse from the output of single-shot D2.3 start the generator reset pulse D3.3. If additional caller picked up the phone, the logic level "1" from the resistor R12 are blocked RS-triggers: D6.1 - in the state of logical "O", and D6.2 - "1".
After finishing the conversation downturn positive pulse start pulse shaper reset D3.3.
Outgoing call primary or secondary subscribers. When lifting the handset of the subscriber, the logic level "1" from the resistor R11 or R12 are set to appropriate state triggers D6.1, D6.2. Locking the telephone of the other party occurs as described above. For more precise work sites VT1; D4, D5 is set, the delay circuit for a period of approximately 10 MS.
The logic level "1" coming from the resistors R11, R12, you can start clock time of the conversation as additional and base of subscribers.
Authors: A. Kisliuk, .Ilyin; Publication: N. Bolshakov, rf.atnn.ru