A5

A5 Front Panel, Circuit Description

The A5 Front Panel comprises the A5Al Keyboard, A5A2 Rotary Pulse Generator (RPG), Instrument Check indicator LEDs, LINE power switch, STANDBY power indicator LED, and CAL OUTPUT connector and cable. The RF INPUT, 1ST LO OUTPUT, and 321.4 MHz IF INPUT and IF OUTPUT connectors are physically part of the A6 RF Module and are described in detail in that section.

A5Al Keyboard

A5Al Keyboard includes the 49 pushbutton switches and 9 associated indicator LEDs on the RF Section front panel.

Keyboard Switches @

Each of the normally open SPST switches consists of a spring-loaded contact and a pair of printed-circuit board contacts. All but two of the keyboard switches are organized in a matrix of rows and columns. When a front-panel key is pressed, the corresponding SPST switch is closed, connecting a normally grounded key row to a key column. The grounded key column signal is detected on the Al2 Front Panel Interface, signalling the Al5 Controller to immediately halt the sweep. Then, the Al5 Controller polls (grounds) each of the key rows sequentially (starting with key row 0) to identify the particular front panel key that is pressed. During normal operation, the front-panel SWEEP LED can be observed to blink off momentarily as the Al5 Controller halts the sweep, polls both the IF Section keyboard and the RF Section keyboard, and then reacquires phaselock before continuing on with the sweep.

Indicator LEDs @

The nine keyboard indicator LEDs and the two INSTR CHECK indicator LEDs are lighted selectively by the Al5 Controller to indicate the state of coupled functions, SIGNAL TRACK (on/off), DATA entry (enabled/disabled), HP-IB control status (remote and addressed), and self-test. U2 and U3 latch the LED data from the Data Bus. All front-panel LEDs are lighted momentarily during the turn-on self test for verification.

The two INSTR CHECK indicator LEDs are lighted selectively by the Al5 Controller to indicate the overall results of the most recent instrument self test. An instrument self test is performed each time the LINE switch is switched to ON or the (INSTR PRESET] key is pressed. Both LEDs are lighted at the start of each self test, and both are turned off upon successful test completion; if one or both of the INSTR CHECK LEDs remain on, an instrument fault has been detected. Refer to the Al5 Controller section for detailed information about the self test.

A5 1