DIP Switch S1 Settings, S1-4 Echo Mode

To access the Model 1008’s internal PC boards, insert a small flat- blade screwdriver between the connector and the lip of the case and twist gently as shown in Figure 3 (below).

Figure 3. Opening the Model 1008’s plastic case with a small screwdriver

Both DIP switch S1 and S2 are marked with individual switch numbers 1 thru 4. Use these numbers, as well as the “ON” designation to orient the switch properly (see Figure 4, below). Use a small screw driver or similar instrument to set each individual switch.

“ON”	ON

“OFF”

Figure 4. Close-up of DIP switches S1 and S2, showing ON/OFF orientation.

3.1.2 DIP SWITCH S1 SETTINGS

DIP switch S1 is used to configure receive impedance, 2-wire/4-wire operation and “echo” enable/disable. The summary table below shows the factory default settings for switch S1. Following the summary table is a detailed description of each individual switch.

SWITCH S1 SUMMARY TABLE (factory defaults in bold)

Position	Function	ON Position	OFF Position

S1-1	RCV Impedance	120 Ohm	16 kOhm

S1-2*	2-wire/4-wire	2-wire	4-wire
S1-3*	2-wire/4-wire	2-wire	4-wire

S1-4	Echo Mode	Echo ON	Echo OFF

*Note: Switches S1-2 and S1-3 should be switched simultaneously

S1-1: Receive Impedance

The setting for switch S1-1 selects the impedance of the input receiver. You may select either a “low” impedance of 120 Ohms or a “high” impedance of 16 kOhms. By selecting the proper impedance for each drop, there may be up to 50 receivers in one application.

S1-1	Setting
On	Low (120 Ohm)
Off	High (16 kOhm typical)

S1-2 and S1-3: 2-wire/4-wire Modes

Switches S1-2 and S1-3 are set together to determine whether the Model 1008 is in 2-wire or 4-wire operating mode. Note: 2-wire mode is half-duplex only.

S1-2	S1-3	Setting
On	On	2-wire mode
Off	Off	4-wire mode

S1-4: Echo Mode

The setting for switch S1-4 determines whether the Model 1008 echoes data back to the transmitting device (half-duplex mode only).

S1-4	Setting
On	Echo On
Off	Echo Off