General
The 21992 Intelligent Repeater utilizes an 8 bit coding scheme. Four preamble bits alert the Repeater that a loop back command is being invoked. Four address bits allow individual addressing of up to fifteen repeater points along a span.

Functional Description
The desired address is selected via a 4 position dip switch.
The table below lists all the Repeater dip switch settings and the looping codes.

S239A Loopback Repeater
	Num	Dip Switch Position	Address Results		Num	Dip Switch Position	Address Results
	0	0000	11000000*		8	0001	11001000
	1	1000	11000001		9	1001	11001001
	2	0100	11000010		10	0101	11001010
	3	1100	11000011		11	1101	11001011
	4	0010	11000100		12	0011	11001100
	5	1010	11000101		13	1011	11001101
	6	0110	11000110**		14	0111	11001110
	7	1110	11000111		15	1111	11001111

*Note: The looping code {11000000}is not recommended because it is
counterfeited by a continuous sequence of HDLC flags.

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**Note: The looping code {11000110} is not recommended because it is
counterfeited by a continuous sequence of B8ZS bytes.

All of the looping codes described above are repetitive eight-bit patterns. The corresponding loop down code is a repetitive five-bit pattern: 11100. The loop down code used for the R C Concepts, 21992 Intelligent Repeater uses the same loop down code that is specified for looping down a network interface(NI).
The Intelligent Repeater also offers powering and fault locating options which are selected via jumpers. For powering options the repeater can be set for either loop or thru power.
For fault locating options, the repeater can be set for common, separate, or no fault locating.