Three Major Development Stages of PCM

📅Oct 10, 2012

Brief：Three Major Development Stages of PCM From an overall perspective, the development of PCM equipment seems to be moving toward a new stage. The PCM equipment of the past has clearly gone through several stages. The first stage of PCM equipment development: only voice services were transmitted, and the transmission interface was an E1 electrical interface, available in 75-ohm and 120-ohm versions.

From an overall perspective, the development of PCM equipment seems to be moving toward a new stage. The PCM equipment of the past has clearly gone through several stages.
The first stage of PCM equipment development: only voice services were transmitted, and the transmission interface was an E1 electrical interface, available in 75-ohm and 120-ohm versions.

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The third stage of PCM equipment development: the service interfaces are basically the same as those in the second stage, with video transmission interfaces and voice developing toward high-fidelity, and the number of various service interfaces increasing; the transmission interface is no longer a pure E1 optical/electrical interface, but is replaced by [SDH](

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