Chen Hao tossed the marker into the pen holder, the tip striking the metal edge with a soft click. He stared at the green wavy line on the screen, which had been steadily extending for nine minutes, like a rope that refused to break.
"How long can this thing run?" he asked.
Nana didn't turn around. The robotic arm was plugged into the host port. "Based on the current load, it will enter the heat warning zone in four hours and thirty-seven minutes."
"That's not what I'm asking." Chen Hao walked to the other side of the control panel, pointing to a red dot on the map. "How far can our signal carry now? Is 8.5 kilometers a dead end?"
Susan looked up. "You want to fight outside?"
“What’s the point of just listening to it yourself?” he said. “We’ve been steadily operating our tricycles for a while now. If we don’t find something to do, the equipment will start to grow mushrooms.”
Carl straightened up from behind the server rack, still holding the temperature gun in his hand. "If you want to send signals to distant areas, you need to increase the power. This power supply won't last much longer."
“I know it’s fragile.” Chen Hao pulled up the data panel. “But look at the last test. When version V2.1a was running at full load, the peak output only used 82 percent of the rated output. That little bit of headroom is enough for us to catch our breath.”
Nana finally turned around, her optical lens aimed at him. "The knowledge base shows that planetary curvature and geological shielding effects accelerate signal attenuation. If the target area is located at a distance, conventional continuous waves cannot penetrate it."
“So we can’t just charge in.” Chen Hao picked up a whiteboard marker and drew a diagonal launch trajectory on the screen. “We’ll change it to a pulse, short and high-intensity, and launch it in a directional manner. Like… throwing a stone over a wall.”
“Whether there’s anyone behind the wall to answer is another matter,” Susan said.
“We have to throw it out first,” he said. “Just in case there are other people over there with stones, waiting to hear the noise.”
Nana connected to the computing module and, a few seconds later, projected a set of parameters. "It is recommended to use a 3.7 millisecond pulse width, with a transmission window every three minutes. Combined with the antenna array focusing gain, the effective radiated power can be increased by sixteen times."
"It doesn't sound like human language, but I think it's reliable." Chen Hao looked at Karl. "Can you lock the angle? Don't deviate by half a degree."
Carl is already adjusting the calibration procedure. "As long as you don't let me change five parameters at the same time, this is my job."
Susan opened the listening protocol editor. "I'll set up an automatic capture thread. As soon as a response signal that matches a periodic pattern is received, an alarm will sound immediately."
"Don't set it too sensitive," Chen Hao said. "Last time, the antenna was blown by the wind and triggered a level three alarm."
“This time, we’ll add a signature comparison,” she said. “We must include a protocol header; otherwise, we’ll treat it as noise.”
The preparation took forty minutes.
The power supply switched to dual-path, the cooling system was connected to the backup circulation line, and the antenna array completed its final angle fine-tuning. A countdown timer popped up on the screen.
"Are we really going to do it?" Susan asked.
"Why not?" Chen Hao pressed the confirmation button. "Initiate the first round of launches."
The main control screen flickered, and the waveform graph suddenly spiked, remaining at zero for ten seconds before returning to normal. The whole process felt like someone had suddenly stepped on the gas pedal and then released it.
“Signal sent,” Nana reported. “Target bearing: 63 degrees south latitude, 119.2 degrees east longitude.”
"What do we wait for next?" Karl leaned back in his chair.
"Wait." Chen Hao sat down, then stood up again. "It's not just about waiting. Check the power supply temperature."
"The main module rose by 1.8 degrees, which is within the normal range," Nana responded.
“Then keep sitting,” he said. “Whoever falls asleep first is responsible for recording the next round.”
No one responded.
Only the low hum of the machine remained in the room. The timer ticked slowly, and three minutes later, the second pulse signal was emitted.
The third round, the fourth round, the fifth round...
Half an hour had passed by the end of the sixth round.
"Still no movement." Susan looked at the monitoring interface. "The surrounding frequencies are very clean."
"I didn't really expect to hit the target on the first shot." Chen Hao leaned against the table. "Even if they have equipment over there, it might not be turned on, and it might not be pointed this way."
“Or it was already scrapped,” Carl said.
“Then let’s just say hello to the scrap metal,” Chen Hao said. “At least it proves there are still living people here who would press the button.”
After the seventh round of signal transmission, they began taking turns monitoring the screen.
Nana maintained the connection, monitoring the link feedback in real time. Her voice prompts sounded every few minutes: "No return signal," "Background noise level is stable," "Antenna phase has not drifted."
Two hours later, Carl yawned.
“I suggest a halt,” he said. “Continuous launches put cumulative stress on the components, and we don’t even know if the other side has a receiver.”
"Let's try two more rounds." Chen Hao didn't look at her. "If six hours isn't enough, then eight hours. We have to run through all the probability tests."
“You’re gambling,” Susan said.
“I’m always gambling,” he said. “Before, I gambled on which parameter would happen to prevent it from exploding; now I gamble on whether anyone on the other side is also gambling.”
The eighth signal was issued.
The ninth round.
The tenth round.
At one point, the power module temperature approached the threshold, and Nana automatically activated the cooling redundancy scheme, temporarily cutting off unnecessary loads to maintain the launch rhythm.
Four hours have passed, and the monitoring interface remains blank.
Susan rubbed her eyes. "Should we lower the firing frequency? Change it to once every five minutes to reduce the burden."
"Don't move," Chen Hao said. "If the rhythm is disrupted, it's easier to miss a response."
"So how long do you plan to stay here?"
"Keep it running until it does," he said. "Or fix it until it does."
This sentence silenced the room for a few seconds.
Then Carl said in a low voice, "You're such a lazy and stubborn person."
"You have to use your strengths in combination," Chen Hao grinned.
The fifteenth launch was completed in the fifth hour.
Suddenly, Nana's indicator light turned from blue to yellow.
"An abnormal signal has been detected."
Everyone sat up straight instantly.
“The source direction is consistent with the target area,” she continued. “The duration is 4.1 seconds, containing seven sets of equidistant pulses, with an interval error of less than three per thousand.”
"Is it interference?" Susan asked.
“Excluding natural sources.” Nana pulled up the spectrum graph. “The signal carrier is stable, with narrowband modulation characteristics, and the repetition pattern conforms to artificial coding logic.”
"Release them," Chen Hao said.
A short, rhythmic "beep-beep-beep" came from the speaker, unlike random noise.
"Play it again."
The sound rang out again.
“This is…” Carl stood up. “Isn’t this the beacon format our early exploration teams used?”
“It’s an older version,” Nana analyzed. “It belongs to the third-generation automated signaling protocol, which is usually carried on remote detection units or fixed observation stations.”
“In other words…” Susan looked at Chen Hao, “there is something alive over there, and it knows how to call out to others.”
“It’s not just alive.” Chen Hao stared at the screen. “It can also understand what we’re saying.”
"Prepare for the next launch," he said. "This time we'll give it a full handshake sequence."
"It's not advisable to reveal too much information before confirming the respondent's identity," Nana cautioned.
“Then send the most basic one,” he said, “the ‘Are you okay?’ kind.”
"This protocol option is not available in the system," she said.
“Let’s make one,” he laughed. “Use binary, one for good and zero for bad. Let’s start with a string of ones.”
Susan inputs a command to set the response signal to eight consecutive high-level pulses, representing the simplest confirmation response.
Countdown begins.
Three minutes later, the launch window opened.
The signal is emitted.
They were all staring at the receiving screen.
A minute passed.
Two minutes.
Just three minutes later, Nana's indicator light flashed again.
“Capture response signal”.
"What content?"
“An eight-bit pulse sequence.” She paused for a second, “all high.”
No one spoke in the room.
After a few seconds, Carl whispered, "It says it's okay."
Chen Hao slowly sat down.
“It wasn’t luck,” he said. “There were genuinely people listening.”
Susan had already started recording timestamps and signal characteristics. "Should we continue interacting? Try to establish a stable link?"
"Let's not move for now." Chen Hao waved his hand. "Let it wait too. We've only just gotten through to the first few words, let's not start by asking where they live and how much money they have in their bank account."
"What's the next step?" Nana asked.
"Continue sending messages at the same pace," he said. "Six times a day, ten seconds each time, in a fixed pattern. Let the other party know that we didn't just randomly scan them."
What if the other party escalates their response?
“Then let’s go up together,” he said. “One step at a time. Anyway, we know now that it’s not just the wind that’s making noise on the other side of the wall.”
Susan stored the data in a log file named "First Cross-Regional Communication Record".
Karl rechecked the physical locking status of the antenna array and confirmed that it was secure.
Nana started running the signal tracing model to try to estimate the location range of the other party.
Chen Hao stood in front of the control panel, tapping his fingers on the table in the same rhythm as the pulse he had just received.
Suddenly, he spoke.
"What do you think we should do if it suddenly asks us, 'Who are you?'"
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