Inmac clear signal tristate tester

Tester for serial line connections. There are several devices from Inmac, this is the 8363-1 with internal battery suppy (9 volts battery). Other models are “passive” and have no own power supply.

Allows to test 1:1 and cross cables via dip switch.

1:1 means pin 2 is connected to pin 2 and pin 3 connected to pin 3. cross cable means 2 is connected to 3 and 3 connected to 2.

Each of the 25 pins can be connected or left open via dip switch.

There are also tiny connectors for each pin on both sides to have arbitrary connectivity between signals. And also pins providing +V and -V signal levels.

One pin called “EIA test” with unknown function. I have no manual for this tester.

The transparent LEDs are dual color (green+red).

User interface

RS232 signal pins:

Inside the tester. 3x TL064 and 1x TL062, 4x and 2x OpAmps, in total 13 OpAmps, I suppose for analyzing signals without give a burden to the signal. One ICL7660, a common chip for creating a negative voltage from a positive voltage (supposed to create the ~ -15 volts for RS232 “HI” level). Impressive amount of 8 resistor networks.

Bottom of PCB.

All packaged in a small stable plastic box.