The Model 1883 is a dual NIM width module containing a 100MHz BCD scaler with eight digit capacity. Visual readout is provided on eight in line LED 7 segment displays. A five (5) digit preset output is available from the 100MHz scaler which is preset to N x 1000 counts. The preset output does not interfere or alter the normal function of the scaler. To accommodate presets of N x 1 the first three (3) digits of the scaler (called prescale) are dis- abled and the scaler becomes a five (5) digit 3MHz scaler. Both the scaler and preset are initialized by the counter reset. When the scaler reaches the number set on the preset thumbwheels a preset level is generated both in CAMAC and NIM logic levels. In addition a NIM pulse is generated. When these outputs occur an LED light indicates a preset coincidence. The preset levels will remain until the scaler is reset.

SPECIFICATIONS CAPACITY Eight digits BCD plus overflow. SIGNAL INPUT Pulse Repetition Rate 0 to 100MHz min.(125MHz typical) with prescaler enabled. 0 to 3MHz min. (5 MHz typical) with prescaler disabled. Pulse Pair Resolution: 10 ns minimum with prescaler enabled. 40 ns* minimum with prescaler disabled. Minimum Pulse Width: 3 nsec FWHM Discriminator Level: -500mv (internally adjustable to a min. -300-mv) Input lmpedance: 500 +/- 10% D.C. coupled Input Reflections: Less than 10% for Ins rise time of NIM level signals. GATE Manual: Front panel three position switch (OPEN,REMOTE,CLOSED) for controlling the counting gate. In the remote position electrical gate signals con trol the counting gate. Electrical: Two bridged LEMO connectors on Front panel. Bridged inputs allow daisy chaining of gate signals from to scalar to saclar *Repetition rate of pulse pairs should not exceed 5MHz (typical). Input Impedance: 5K min. Sensitivity: -500mv Input Protection: t 50 volts transients Response Time: Less than l0nsec. RESET Manual: Front panel push button for reset of,counter overflow, display and preset level outputs. Electrical: Two bridged LEMO connectors on front panel. Bridged inputs allow daisy chaining of gate signals from scaler to scaler. The input is bias- ed to a CAMAC logic zero (approx. 3.5v) and a ground or a current sink of 3ma will generate a reset. DISPLAYS Counter: Eight in line "1/8" high character LED seven segment digits. Three least significant digits are blanked when prescaler is disabled. Gate: LED light on when counter gate is open. Overflow: LED,light on when counter overflows. Turns off when counter is reset. OUTPUTS Carry Output: LEMO front panel connector provides a fast NIM pulse -800mv into 50 ohms each time counter overflows. A carry pulse will not be generated at reset. PRESET Prescaler Select: Two position toggle switch enables or disables the three least signifi- cant counter digits. Input: A five digit thumbwheel is used to set the preset number. Preset num- ber is N x 1 when prescaler is dis- abled and is N x 1000 when prescaler is enabled. Preset Output: When scaler reaches the preset number, the preset LED light is illuminated and the preset electrical outputs are activated. CAMAC Level Output: At preset coincidence a CAMAC "1" (O to .4 volts) is generated at the A Lemo connector. A CAMAC "10" (+2 volts at lma) is' generated at the A Lemo con- nector. These outputs are capable of sinking 48ma at logic "1". NIM Level output: At preset coincidence a -900mv minimum signal into 50 ohm signal is generated at the B Lemo connector. A complemen- tary signal of 0 t 50mv into 50 ohms is simultaniously available at the Lemo connector. NIM Pulse output: At preset coincidence a 50 nanosecond (-900mv into 50 ohm) pulse is generated at the C Lemo connector. Preset Propagation Delay: Preset outputs will be generated, 350 nanoseconds (typical) 500 nanoseconds (max.) after coincidence. P0WER Requirements Less than 12 watts + and - 6 volts Option 1: -12 volts and 115 volt a-c- Temperature RANGE: 0 to 60 C SIZE: Double width 8 3/4 high NIM module.