Telegraph equations, can be looked as cascade connection of two-port network of lumped circuit of transmission line, is a hyperbolic partial differential equations.

传输线可以看作集中参数二端口网络的级联，其数学模型—电报方程是一阶双曲型偏微分方程组。

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But it was only with the growth of the electric telegraph network in the 1850s that readings could be collected from a wide area quickly enough to follow the weather as it changed.

ECONOMIST: Weather maps

Field, the New York exchange denied telegraph access to any outsiders who didn't route orders through a network owned by the exchange.

WSJ: New Twist Is Added to an Age-Old Saga