Global Specialties PB-505 - Manual - Manual (Page 11)

11
In addition to the DC power supplies, the PB-505 also provides a 12.6 volt center-
tapped AC supply. This allows the user to construct any of half-wave and full-wave
rectified power supplies on the breadboarding area and apply power by simply
connecting jumper wires to the three AC supply output pins.
FUNCTION GENERATOR
The multi-waveform function generator provides continuously variable frequency signals
from 0.1Hz (for extra-low frequency work) to radio frequency signals of 100Hz. The
frequency is selected in six decade ranges, with a vernier to adjust frequency within
each range. The sine wave output is factory adjusted for minimum distortion. The
triangle waveform is adjusted for best linearity. The standard square wave and TTL
level outputs are both set at a 50% duty cycle. The TTL output (available when the
function generator is set to square wave), capable of driving up to 10 TTL loads, is
continuously available and in phase with the square wave output. The low output
impedance of the sine, square, and triangle waveforms (600 ohms) assures maximum
coupling of the output signal to the device being driven. All outputs can withstand a
continuous short circuit to ground.
LOGIC INDICATORS
Sixteen LED's, eight red and eight green, make up eight Logic Indicators that will
display logic high and low conditions based on either TTL or CMOS thresholds,
selectable by the user. Operating voltage can also be selected by the user to be either
at +5V, or at the setting of the +1.3 to +15V supply. This selection should be the same
as the operating circuitry that is to be monitored. The red LED's will light when the
voltages at the inputs are 2.2 volts or higher when in the TTL position, or 70% of the
operating voltage or higher when in the CMOS position. The green LED's will light when
the voltages at the inputs are 0.8 volts or less when in the TTL position, or 30% of the
operating voltage or less when in the CMOS position. An unconnected input, or an input
not at valid logic level, will cause both LED's to be extinguished. Note that the
thresholds determined by the TTL positions are only accurate when the +5V range is
selected. The 100K ohm input impedance ensures minimal loading effects of the circuit
under test.
DEBOUNCED PUSHBUTTON (PULSERS)
The PB-505 uses clocked flip-flops to provide debounced pushbutton switch functions.
The pushbutton circuitry has open-collector outputs switch can sink up to 250mA each.
This type of debouncing gives the user a sharp, glitch-free trigger source which assures
reliable operation in digital circuits. Each pushbutton has a normally-open and a
normally-closed output. If necessary, a pull-up resistor can connect any pulser output to
any of the positive voltage sources.
POTENTIOMETERS
Two potentiometers are provided on the PB-505. The resistance values chosen (IK and
10K ohms) may be used in common circuit applications such as volume controls. All
leads for both potentiometers are available and uncommitted.