gating signal. The output pulse train begins with the gate signal. For fixed width gate sig- nals, a constant number of outputs will be gated on for a given internal frequency.

In ASYNC mode, the internal clock free runs and the signals from the clock are gated. Thus, the beginning of the gate may occur before, during, or after the occurrence of an output pulse.

Gate signals will gate SINGLE CYCLE, internal FREQUENCY, and EXTERNAL TRIGGER sig- nals. The gate will operate in ASYNC mode on any of these trigger sources. In SYNC mode, the gate will operate on SINGLE CYCLE or internal FREQUENCY signals.

2. 2. 6 TRIG OUT
This connector provides a trigger signal to which pulse delays are referenced. The 50% point of the positive sloped edge is the zero delay point. The trigger level is about +1 V into 50 Ohm. The TRIGGER OUT circuitry is a current source of about 20 mA that will sat- urate into high impedances at a level of about +4. 5 V. A 50 Ohm load should be used when work- ing with narrow delays. With an internal clock, the output is a square wave. In the EXT/S. C. model. if an EXTERNAL TRIGGER is applied, the TRIGGER OUT follows the EXTERNAL TRIGGER width; if the S. C. pushbutton is pressed, the TRIGGER OUT is 70 ns wide.

2.2.7 DELAY

This concentric switch/potentiometer control determines the delay between the leading edge of the trigger signal and the leading edge of the output pulse. Together with the nine coarse ranges, the vernier control provides for con- tinuous adjustment of delays from 25 ns to 1 s.

2.2.8 WIDTH
This concentric switch/potentiometer combina- tion controls the width of both output pulses. The output pulse begins at the end of the delay time and ends after a time determined by the WIDTH controls. The nine coarse ranges, to- gether with the vernier- control, provide for a continuous width adjustment from 20 ns to 1 s.

2.2.9 SINGLE PULSE/DOUBLE PULSE
The S. P. / D. P. toggle switch selects single pulse or double pulse operation. In the SINGLE PULSE mode, the output pulse starts after the DELAY time and lasts for a duration deter- mined by the WIDTH controls.

In the DOUBLE PULSE mode, two pulses oc- cur: one starts at essentially zero delay (at the positive slope of the trigger signal) and lasts for a duration set by the WIDTH controls; the other pulse occurs after the delay tin-ie for a duration set by the WIDTH controls. In the DOUBLE PULSE mode, the spacing between the two pulses is determined by the DELAY setting, and the width of both pulses is deter- mined by the WIDTH controls. In the DOUBLE PULSE mode, both the width and the delay should be at least 20 ns for proper operation.

2.2. 10 NEG OUT
The . 8 V/1. 5 V toggle switch allows the selec- tion of one of two forms of negative outputs. With the toggle switch at . 8 V, a fixed -0. 8 V pulse into 50 Ohm from a 0 V base line is selected. This is the standard fast NIM logic.
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