The Relay Spliced Into the Line

The foreign-made solder gleamed damp even though it hadn't rained yet. Jang Munsu had already confirmed that a hidden relay existed. His job today wasn't to attach a name to whoever had installed it. It was to measure how much signal was being drawn off, and from which section. Get it wrong, and he could cut off their own line, or spread a false signal as if it were a real order.

Three wires ran into the inspection post on the outskirts of Hanseong. The official telegraph bureau line, the northern relay line, and a thin copper wire that came out from behind a wall board. Jang Munsu tagged all three ends with numbers.

"First, we disconnect the battery and measure natural resistance. Second, we send a short test signal. Third, another operator retests the same value."

A constable sent by Im Gwanpil asked, "If it's a foreign screw thread, foreign quartermasters must have put it in, right?"

"That's a guess."

Jang Munsu pressed the screw head's groove into paper to take an impression. "This is a trace."

He didn't open the relay's cover yet. First he measured the official line's resistance. It was higher than on dry days. Rain clouds moving in could mean the insulation cloth had absorbed moisture. When he disconnected the thin copper wire, the value dropped slightly.

"So the secretly attached wire is drawing off signal, right?" the constable pressed.

"One reading doesn't tell us that."

Jang Munsu replaced the insulation cloth with a new one and measured again. The value dropped again, but not enough to account for the whole first difference. Moisture and the relay were both having an effect.

"It's not just the moisture."

"Then who's the culprit?"

"A measurement doesn't have a culprit's name in it."

He examined the solder marks with a magnifying glass. The official telegraph bureau's solder was gray and rough. The solder on the hidden wire was brighter and smoother, and the resin smell was different. It was likely foreign material. But the merchant who sold the material, the technician who installed it, and the organization that used it could all be different people.

The inspection post door opened and Yun Haejun walked in. His bindings hadn't been removed, and two inspection constables followed him.

"What's left?" Haejun asked.

"The scope of the duplication, and the delay time. We don't know who installed it."

"Was the first forged telegram duplicated?"

"Some of the dot and dash groups remained on the paper tape. We'd need to retest to know if it was the whole message."

The moment Haejun saw the hidden line, he didn't say to cut it. "Can we use the fact that it's being intercepted?"

Jang Munsu's hands stopped moving. "What do you mean to send?"

"A limited false signal. Leak a short line saying the army provisions are moving to Seogang ferry landing, and see who starts buying up carts and horse feed."

The constable laughed. "That's good. Fool the enemy."

"Not good yet," Jang Munsu said. "We don't know which direction the hidden line runs. And if the false signal also reaches the official relay station, our own carts could actually move."

Haejun asked, "Can they be separated?"

"A test signal, yes. An execution order, no."

"What's the difference?"

"We give the official recipients a verification code beforehand, something to mark it as a test. Then we see whether only the phrase without that code gets duplicated on the hidden relay's side."

Haejun thought for a moment. "Who holds the verification code?"

"Two telegraph bureau operators and an inspection witness. You shouldn't hold it."

"Even though I proposed the false phrase?"

"Precisely because of that."

Haejun didn't argue. If he held the code that separated real content from fake, he'd once again be the one locking up the decision alone.

Jang Munsu divided the test procedure into three columns on paper. Measured facts, his own interpretation, proposed political use. In the first column he wrote only the resistance values and the state of the solder. In the second he wrote, "High likelihood of duplication, direction and installer unconfirmed." In the third he wrote out Haejun's false signal proposal exactly as given, and boxed it with the words: not to be executed before approval.

"Who does this document go to?" Haejun asked.

"Inspection, the telegraph bureau, the northern relay station. Three separate operators retest it independently."

"And the Qing technical network?"

Jang Munsu's brush paused for a moment. Some of the instruments and insulation cloth he used had been learned from Qing technicians. Asking about part numbers could narrow down the source faster. But if the original measurement fell into their hands first, it would blur which country held the evidence.

"We don't send the original. Only questions about part dimensions and solder composition. We require the source and the author's name with any answer."

"What if they attach conditions?"

"We disclose the conditions along with the answer."

The constable clicked his tongue. "The wire doesn't know borders, but customs knows copper."

Jang Munsu looked at him. "I made that joke first."

A short laugh passed through the inspection post. Then a raindrop struck the roof.

Jang Munsu began the first test. On the official line he sent two short dots, one long dash, then two dots again. The telegraph bureau's receiver attached the verification code he'd been given in advance and sent it back. The round trip on the official line took twelve beats.

After finishing the first test, Jang Munsu turned the measurement sheet face down. He called in Choe Seokgu, the retesting operator, but told him neither the earlier values nor that a hidden line existed.

"Measure the three wires in order. Don't try to find anything unusual. Just write down the values that come out."

Choe Seokgu took off his wet shoes and wiped his hands with a dry cloth. He replaced the battery contact surface once, and pressed the moisture from the insulation cloth with a dry cloth of the same weight. On the first wire he got a reading one notch higher than Jang Munsu's, on the second the same, and on the third one notch lower.

The constable said, "The values are different, isn't that a failure?"

Jang Munsu held out the tolerance chart. "There's human hands and moisture involved. If the exact same number came out, that would actually mean he'd seen the first value beforehand. All three are within range."

Choe Seokgu looked at the hidden line's solder and asked, "This wire isn't in the ledger?"

"No."

"Then in my report I'll write only 'connection outside the ledger.' The word 'foreign made' goes on after we compare materials."

Jang Munsu didn't correct that sentence. Another operator not copying even his interpretation was the whole point of retesting.

The paper tape at the end of the hidden line moved six beats late. The same dot and dash groups were printed, but there was no verification code.

"It duplicates," Jang Munsu said. "At least in this section."

"Where does it go?"

"Still don't know."

In the second test he sent an empty phrase, a signal with the same length but no content. The hidden line's paper tape moved along with it too. The device wasn't selectively listening for meaning. It was closer to copying the entire incoming current.

Haejun asked, "So the limited false signal would go through too?"

"It would. The official receiver would get it too."

"We can filter it with the verification code."

"Only if the operator knows the code and keeps to it."

Thunder rolled outside. The courier heading to the northern relay station saw the rain and stopped in his tracks. To verify fast communication, a person had to walk the muddy road and deliver the code first.

The courier was wrapping straw rope around his straw shoes when he asked, "If we lose the code, can we not use the line at all?"

"Not until word comes back that it was lost," Jang Munsu answered.

"Then if my round trip is late, Hanseong stops."

"That's why we record departure and arrival times, and the names of anyone traveling with you."

The courier chose a messenger who knew the road as his witness. Jang Munsu sketched the straw knot patterns on both men's shoes and attached the drawing to the back of the envelope. If someone were swapped along the way, the feet would give it away before the documents did.

After the two men went out into the rain, the clock at the inspection post struck once. From that moment the official line was sealed until the verification code arrived. Even urgent dispatches guarding the standoff would have to wait the same half hour.

Jang Munsu wrote the costs next to the false signal proposal. Two hours for the courier's round trip. Half an hour of the northern line stopped. Possibility that own carts move if misread. Possibility that whoever's on the other end of the hidden line notices the test.

Haejun said, "Let's still do it."

"Who approves it?"

"Inspection and the telegraph bureau operators. The cart representative on the ground needs to see the wording too."

"Why the cart representative too?" the constable asked.

"If a false movement of army provisions drives up real prices, they're the ones who pay for it first."

Jo Mansik, the Mapo cart representative, was called in. He read the draft of the false signal and struck out the first line with his brush.

"'All army provision carts to Seogang.' The word 'all' won't do. If the horse feed merchants hear that and triple the price, even empty carts will be pushed toward Seogang."

Haejun asked, "How far will you allow it to go?"

"Two test carts. No actual departure. Inquiry about contracts only. No advance payment for feed."

"Then won't the other side see it as bait?"

"That's your calculation. Horses going hungry is mine."

Jo Mansik wrote a stop condition next to the draft. If even one cart actually moved, or if feed prices rose past double the usual, the line would be cut immediately. He wrote his own name and the numbers of two carts, then signed it.

Haejun crossed out "all" and revised it to "two carts, contract inquiry only." As the scale of the deception shrank, so did the information they'd get from it. But the risk of the test collapsing local prices shrank too.

"The call to stop belongs to Representative Jo," Haejun told the constable. "Even after inspection approves it, it can be cut off on the ground."

Jo Mansik didn't nod. Only after reading the revised wording through to the end once more did he hand it back to Jang Munsu.

Jang Munsu noticed his own habit of trying to push political questions outside the circuit. Even if the signal was false, the rising feed prices and the cart drivers caught up in it were real.

"I'll write down that condition."

Below the approval box he added the cart representative's right to review and to stop the operation. If the false signal went beyond the scope of the test, the representative on the ground could cut the line.

The third retest was handed to yet another operator. The young operator measured the resistance without looking at the figures Jang Munsu had written, and sketched the solder marks separately. The values weren't identical, but they fell within tolerance.

Only then did Jang Munsu write at the top of the report: External relay connection and partial signal duplication confirmed. Installer and destination unconfirmed.

The constable asked, "You're not writing 'foreign quartermasters'?"

"If I write that, a guess takes the place of a fact."

Haejun nodded. "Send that report and the false signal proposal separately."

"What about your name?"

"Only on the proposal. On the measurement report, only Jang Munsu's name and the retesting operators' names."

Jang Munsu put the two documents into separate envelopes. He made sure the technical facts wouldn't become ornamentation proving Haejun's plan.

The rain grew heavier. The courier bound for the north wrapped more straw around his shoes and set off. The official line stayed shut down until the verification code arrived. The hidden line was sealed, not cut.

Just then, outside the inspection post, a cart carrying the wounded came to a stop. Word had come that an empty warehouse was being turned into a temporary aid station. Behind the cart sat Yun Sunhwa, asking each patient's name one by one.

"Tell me the time you were injured too. And if there was an order you received then, that as well."

Through the doorway, Jang Munsu saw her ledger. Beside each person's name, a time and an order were being written in.

It was slower than a signal duplicated over the wire, but that ledger would keep a far more accurate record of who had paid the cost of that signal.