Li You mentioned in the letter about the manipulation of currency, Li Shimin thought it was an extremely important matter, he wanted to hear Li You's opinion in person, of course, this was just a reason, he really wanted to see his son in his heart.

Thinking of this, Li Shimin immediately ordered someone to be sent to Kabul to deliver the decree and let Li You return to Chang'an.

After the Tang army destroyed the Feituo Kingdom, the border patrol team of Tubo spotted the patrol soldiers of the Darobitu people on the opposite side, and suddenly became Tang Dynasty people overnight, and they were very surprised for a while.

The soldiers of the Tang Dynasty would escort the envoys of the Tang Dynasty, and with the consent of the Tusboans, they entered the border of the Tusboans and headed for Lhasa.

Songtsen Ganbu saw that the Tang Dynasty's occupation of the Feituo Kingdom had become a fait accompli, and he was helpless.

The Feituo Kingdom was originally the main channel for trade between Tusi and Tianzhu, but now it was blocked by the Tang Dynasty, and they had to accept Li You's suggestion to trade with the Tang Dynasty.

Li You invited the Tibetans to continue to maintain economic and trade ties with the newly established Baijistan region and the Angot province.

The newly established Tang Dynasty Bajistan trade channel continued to be open to the Tu S people, and at the same time the Tu S Tibet was open to the Tang Dynasty's trade route, so that the Baji Stans could go directly to Chang'an through the Tu S Bo, which was nearly 1/3 shorter than the Silk Road through the Western Regions.

This would greatly deepen the trade between the Tang Dynasty and the countries of mainland India.

So far, the Tang Dynasty and Tubo have maintained a state of peace and tranquility.

Annoyed that the Tang Dynasty had occupied their vassal states, the Tianzhu Kingdom sought quarrels and provoked trouble on the border, and as a result, they finally gave up their attempt to recapture the Feituo Kingdom under the counterattack of the Tang army.

Then Wang Xuance sent an envoy to Tianzhu and reached an agreement with the king of Tianzhu on trade and trade.

So far, the Tang Dynasty and the Tianzhu Kingdom have also maintained a state of peace and quiet.

Li You decided to spend a year digesting the newly occupied areas and not to expand externally for the time being. The situation has calmed down.

Kabul city.

The affairs of Bajistan and Angot Province were worried about by the military and political officials, and Li You was idle.

While enjoying the food with his wife, Li You focused on the study of radio communications.

This matter is too difficult, mainly because the industrial base in the Kabul area is so poor that not even a single copper wire can be processed.

Li You organized a large number of craftsmen to work hard to achieve their goals.

Through Li You's lectures, the trainees of the wireless telecommunications training course showed them a brand-new world of science and technology, which greatly stimulated their enthusiasm for studying scientific and technological knowledge. In addition to studying, they worked with the craftsmen to study and build the telecommunications equipment that Li You said according to the drawings drawn by Li You.

Building a radio station was not an overnight task, and Li You first had to deepen the students' and craftsmen's understanding of electricity.

On this day, Baihu took a set of expensive glass tea sets and sent them to the craftsmen's workshops, and Baihu also brought a set of drawings and related instructions.

Baihu said: "The prince has explained, let you process these glasses into the drawings as they say." ”

"This?" The craftsmen were very surprised, this set of crystal bright glassware is definitely worth a lot, and the prince actually let them process it into the half-gourd-shaped thing on the drawing, which is also too loser, well, a waste, right?

Seeing the craftsmen hesitating, Bai Hu said: "Although you do it boldly, the prince said, this set of glassware is for you to use to practice, if it is not enough, I will send it to you again." ”

There were no glass factories in Kabul, so Li You had to have artisans smelt the glassware he brought.

Baihu said very generously, but the craftsmen did not dare to lose like this, they carefully studied the drawings, hoping to save materials to the greatest extent.

On this day, the people in the Kabul Governor's Palace were very excited, and they were expecting a miracle.

In the guest room next to the conference hall, Li Duan and the others were tinkering with a machine.

This machine is the same as the Faraday Disc Generator, the world's first generator invented by electromagnetic induction shortly after Faraday discovered the phenomenon of electromagnetic induction in 1831.

The structure of this power generator is different from that of modern generators, and instead of a coil, a disc made of copper rotates in a magnetic field. A crank handle is fixed at the center of the circle, and the edge of the disc and the center of the circle are respectively attached to a brass brush, and the brush is connected with the ammeter with a wire; The copper disc is placed in the magnetic field of a hoof-shaped magnet.

When the crumble is turned to rotate the copper disc, the pointer of the ammeter is deflected to one side, indicating that a continuous current is being generated in the circuit.

Two wires were connected to the machine, through the cracks in the windows of the guest room, and into the council chamber, where on the beams on the roof of the chamber hung what Li You called light bulbs.

This thing is the light bulb that White Tiger asked the craftsmen to process.

Tungsten lamp, Li You can't make it now, he can only follow the bamboo lamp made by Edison back then. But it's powerful enough to be lit for thousands of hours in a row.

At this moment, in the conference hall, Li You and his wife, Cheng Yanjin, Ma Zhou, Abu Hassan, and others, as well as officials of the palace, gathered large and small. These people got off work, didn't go home, and stayed in the council chamber, waiting for a miracle to happen.

At this time, it was not yet completely dark, and Abu Hassan was anxious, and ordered his servants to draw up all the curtains of the doors and windows, and the chamber was suddenly dark.

Soon after, a bright light came through the door, and Li Duan opened the door and entered. He said, "Lord, the ministers are ready." ”

Li You said: "Then let's start." ”

"Yes, lord." Li Duan retreated and closed the door casually, and it was pitch black inside the conference hall again.

Suddenly, the electric lights hanging from the beams of the room came on, and the inside of the chamber suddenly became like daylight.

Under the strong light of incandescent lamps, people who are accustomed to using candles at night for dim light are suddenly unable to adapt, and many people involuntarily cover or close their eyes.

Cheng Biting Jin was not afraid, he stared at the bulbs on the roof with wide eyes and open mouth.

"It worked." The students of the wireless telecommunications class and the craftsmen who participated in the development of electric lamps were the first to cheer.

Then the people in the chamber erupted in applause and cheers.

The miracle of turning night into day quickly spread throughout the city of Kabul, and people with heads and faces and connections did everything possible to enter the governor's palace to see the rarity.

These days, many people come to Abu Hassan, hoping to catch a glimpse of the magic of electric light. Abu Hassan soon got bored, so he simply asked the craftsmen to erect a flagpole in front of the governor's palace and hang electric lights on the flagpole so that the people could see enough.

For many days in a row, at night, the front of the Governor's Palace was crowded with people, and this craze lasted for a long, long time.

The successful development of the electric lamp greatly stimulated the enthusiasm of the students and craftsmen of the wireless telecommunications study class, and under the guidance of Li You, they made further efforts to develop a radio station.

On the eve of the Shangyuan Festival, Li You received a holy decree from Li Shimin to return to Chang'an.

Li You was going to pass through Tibet on his way back to Chang'an, and by the way, he went to visit Songtsen Ganbu.