8 Options

General

The VT102 uses only one internally installed option, the 20 mA current loop option (VT1XX-CA). This chapter describes the option, its installation, and checkout. See Chapter 10 for ordering information.

20 mA Current Loop Interface Option (VT1XX-CA)

This optional interface connects the terminal to a computer. The 20 mA option consists of a board and interface connector. When this option is installed, you must set the modem control SET-UP feature to FDX A (full-duplex with no modem control). The internal communication switches are not used with the 20 mA option. Figure 8-1 shows the 20 mA current loop interface connector and pin assignments.

NOTE: The terminal uses either the 20 mA or standard modem interface. If you use the standard modem interface with the 20 mA option, unplug the cable connecting the option to the terminal controller board.

Figure 8-1 20 mA Connector and Pin Assignments

Option Installation

Install the option by using the following procedure (Figure 8-1).

  1. Turn the power switch off (0) and unplug power cord.
  2. Unplug keyboard, communication, printer, and composite video output cables.
  3. Loosen the two captive screws holding the access cover in place (Figure 8-2).
  4. Pull the access cover straight out from the back of the terminal, until loose. Then move the cover to the left, off the supporting studs. Finally, remove the access cover by pulling straight out (Figure 8-3).
  5. Install the 20 mA option board in the access cover by using the three Phillips head screws provided (Figure 8-4).
  6. Install the 20 mA connector to the bottom of the access cover by using the two spacers and two hex head screws provided.
  7. Install the 20 mA loopback connector around a spacer holding the 20 mA connector to the access cover. This prevents the loss of the loopback connector.
  8. Set the 20 mA transmit (TRANS) and receive (REC) switches to the proper configuration (Figure 8-5).

    The switches determine if the transmitter and receiver of the 20 mA interface are active or normal (passive). Usually, the switches are set for normal (passive) operation. Passive means the terminal does not supply the 20 mA current used when communicating. Active means the terminal supplies the 20 mA current when communicating.

    NOTE: You must set these switches for normal (passive) operation to perform the loopback self-test. The test verifies operation of the 20 mA option after installation.

  9. Connect the adapter cable provided with the option to the 20 mA board. Place the access cover next to its opening in the back of the terminal. Connect the other end of the adapter cable to the connector on the terminal controller board.
  10. Hold the access cover straight up and move it to the right side of the terminal opening. Push the access cover into the opening and feel for the studs on the right in the terminal. Push the access cover onto the studs until the cover is in place. Figure 8-3 shows how the access cover fits on the studs.
  11. Tighten the two captive screws that hold the access cover in place (Figure 8-2).

    CAUTION: You may damage the access cover by tightening the captive screws too much.

  12. Perform the following option checkout procedure.
Figure 8-2 Access Cover Screw Locations
Figure 8-3 Access Cover Removal
Figure 8-4 20 mA Board Installation
Figure 8-5 20 mA Board Configuration

Option Checkout

The data loopback test verifies the 20 mA current loop option can transmit and receive characters. Characters transmitted during the test pass through the loopback connector back to the terminal. The test checks these characters to verify the option's operation. Perform the data loopback self-test by using the following procedure.

  1. Turn the power switch off (0) and unplug the power cord (Figure 8-1).
  2. Unplug the communication cable.
  3. Install the 20 mA loopback connector (DIGITAL PN 70-15503-00) supplied with the option (Figure 8-6).
  4. Remove the access cover and set the 20 mA TRANS and REC switches by using the following procedure.

    NOTE: Remove the access cover only if the TRANS and REC switches are not set to normal.

    1. Unplug the keyboard, printer, and composite video output cables.
    2. Loosen the two captive screws holding the access cover in place (Figure 8-2).
    3. Pull the access cover straight out the back of the terminal, until loose. Then, move the cover to the left, off the supporting studs. Finally, remove the access cover by pulling straight out (Figure 8-3).

      CAUTION: You may damage the access cover by tightening the captive screws too much.

    4. Connect the keyboard cable.
  5. Turn the power switch on (1). The terminal performs the power-up self-test.
  6. Enter SET-UP and select:
  7. Start the data loopback self-test by using one of the following sequences.
    ESC [ 2 ; 2 y Performs test once.
    ESC [ 2 ; 10 y Performs test continuously.

    The single test displays the wait message while running. The test ends with the following indications.

    The continuous test also displays the wait messages while running. The test ends only when it finds an error or power is turned off.

    When either test finds an error, the terminal displays an error code. An error means the option is not operating correctly. Call your local Digital Field Service Office for assistance.

  8. Turn the power switch off (0) and remove the loopback connector.
  9. If you set the TRANS and REC switches in step 4, select the correct switch settings.
  10. Connect the communications, printer, and video output cables.
Figure 8-6 20 mA Loopback Connector