A complete X21 (comprising X20 and X22) interface "troubleshooter", Testing X26/27, V10/11, RS422/423 electrical standard

COMTEST/Benedict Computer
X.21
Click image below for full size photo
* Breaks and redirects all 15 lines.
* Tri-state monitor on all lines.
* Two additional monitors, one with
  6 thresholds to test secondary signals.
* Pulse trap,with audible sound.
* DC sou
Pulse trap,with audible sound.
rce to set ON and OFF
* RS232 monitor port included.
* Powered by two 9-volt batteries
  or main adapter (not included).

The Comtest X21M is the easiest to use and the most flexible in-line communications tester available, making it possible to test line impedance, voltage strengh and open circuit voltage, giving audible alarm when a threshold is exceeded. Easy to be carried around, this is a time and trouble saving tool for engineers who install and repair X21 equipment.
 

The Comtest X21M has a 15 pole dual-in-line switch with DCE/DTE interface pins on both sides, making it possible to break and crosshatch all lines by means of the switches and the jumper cables supplied with the unit.

The buzzer is a very useful function meant to draw attention to a momentary change or to enable the user to work freely on his interface problem and signaling as soon as the communication starts.

The Comtest X21M is housed in a molded, durable ABS plastic case, with the battery compartment on the backside. The text on the panel is printed in such a manner that the lettering cannot wear off. All contacts are gold plated to ensure good electrical contact.

Open voltage test : Open all switches and connect pin 8 from both DTE and DCE to monitor II.When a certain threshold is exceeded the pulse trap will be triggered and a buzz generated.

Impedance test : The impedance on the X21 interface is not supposed to be lower than 100 ohms. Isolate the active transmitter and connect the DC source to the line which must keep a voltage over 2 volts (our DC source is current protected at 25 mA).

TECHNICAL INFORMATION :

In-line monitors :
Light up green when signal is OFF (mark),<-0.3V
Light up red when signal is ON (space),A-B>0.3V
Monitors I & II :
As in-line monitors, monitor I has a threshold of 0.3 Volts and monitor II has thresholds at 0.2, 0.4, 1.0, 2.0, 4.0 and 8.0 volts.
Pulse trap :
Connected to monitor II, giving it the same thresholds.The pulse trap will store any momentary change exceeding the threshold.
Buzzer :
Connected to monitor II, it will buzz at every change exceeding the threshold, unless switched off.
Battery check :
Shows green light when battery voltage is over 13 volts, which quarantees proper functioning of the Comtest X21.
D.C. source :
2.5 volts D.C., current protected app. 25 mA
To ensure definite state (ON-OFF), both A&B should be connected.
Power :
Supplied by two easily changeable 9 volt batteries, preferably alkaline, giving appr. 8 hours use, or mains adapter (optional).
 
Temperature :
For use :...............................0 to 50°C
For storage :.....................+25 to 70°C
 
Dimensions : (W x H x D) :
165x80x34 mm
6.5x3.1x1.3 inches
 
Weight (with batteries) : 380 g (13.4 oz)
 
Optional :
Mains adapter : 16V/70mA (stabilized).
Extra cable set : 6 single + 2 crosshatch cords.
 
The Comtest X21 comes complete with 8 jumper cables, a user's manual and a small pouch for transport.

 

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