Black Box ME759C-RJ45, ME758C-RJ45, May-95 manual Switch S3 Summary, S3-1 and S3-2 Input Impedance

CHAPTER 3: Configuration

3.1.4CONFIGURATION SWITCH “S3”

Use the individual positions on DIP switch S3 to set antistream control, receive (input) impedance, and point-to-point/multipoint, as well as to enable or disable local and remote loopbacks. The factory-default settings are summarized in Table 3-3 below.

Table 3-3. Switch S3 Summary

Position	Function	Default Setting
S2-1	Input Impedance	On	200 ohms
S2-2	Input Impedance	Off
S2-3	Reserved	N/A
S2-4	Pt.-to-Pt./Multipoint	On	Point-to-Point
S2-5	DTE Local Loopback	Off	Disabled
S2-6	DTE Remote Loopback	Off	Disabled
S2-7	Antistream Control	Off	Disabled
S2-8	Antistream Control	Off

S3-1 and S3-2: Input Impedance

Set positions 1 and 2 of switch S3 to determine the Multi-Function LD Card’s input impedance.

Choose the optimum impedance setting for your application. In long- distance applications, the impedance of the cable must match the impedance of the load (or resistor) of the Multi-Function LD Card: Thicker-gauge cables require a lower ohm setting, while thinner-gauge cables require a higher ohm setting. Also, higher data rates call for a lower ohm setting, and lower data rates dictate a higher ohm setting. Table 3-4 below lists our recommendations for setting this switch.

S3-1	S3-2	Input Impedance
On	On	130 ohms
On	Off	200 ohms (default)
Off	On	320 ohms
Off	Off	High (minimum 2000 ohms)

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