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How Basic Transparent Encoding Works

There are two modes of transparent encoding. They are Transparent 4 mode (TRANS) and Transparent 8 mode (TRANS8). Transparent 8 mode is supported only on CTPOS release 6.4 and later.

Transparent encoding mode 4 samples incoming data on four input signals (SD, TT, RTS, and DTR), transports these signals across the IP network to the remote end of the circuit, and sends the signals on four output signals (RD, RT, CTS, and DSR). Figure 1 shows a simplified model of a transparent encoded circuit.

Figure 1: Simplified Model of a Transparent Encoded CircuitSimplified Model of a Transparent Encoded Circuit

The signal sampling rate is based on the configured port rate. For example, if the port rate is 128 Kbps, then the four signals are sampled at 128 KHz, which generates a packet flow through the IP network of 512 Kbps (4 x 128 KHz). The smallest sampling rate available is 5.3 μsec (approximately 192 KHz).

To prevent errors in transport, both ends of the circuit must be synchronized with each other. You can achieve synchronization either by locking each CTP node to a common reference or by enabling adaptive clocking on one end of the circuit.

Transparent 8 encoding is an extension of Transparent 4 encoding. Compared with Transparent 4 encoding, which sends four signals in each direction, Transparent 8 encoding doubles the bandwidth and allows eight signals to be sampled and transported. This allows signals to be sent from additional interfaces that were not supported in Transparent 4 encoding, although the bandwidth usage will be higher.