Figure 7-13.--Block diagram of the general alarm module.

Figure 7-13.--Block diagram of the general alarm module.

the general alarm contact maker will energize relay

amount of time the alarm will continue sounding after

K302, which will ground all stages fed with -10 volts

the alarm contact maker is released. Normal adjustment

dc. K302 also supplies -30 volts dc to transistor Q307

is for a 15-second hold.

through relay K301, thus energizing K301, which holds

UNASSIGNED A ALARM.-- The unassigned A

K302 energized and supplies control voltage to the

alarm contains transistorized oscillator and timer

amplifier.

circuits that generate 500-Hz and 1500-Hz sine waves

The striking multivibrator also supplies a signal to

alternating at a rate of 1 1/2 Hz, producing a jump tone.

transistors Q203 and Q204 in the chemical alarm circuit,

Figure 7-14 is a block diagram of an unassigned A alarm

causing K202 in the chemical alarm circuit to operate

module. Operation of the unassigned A alarm contact

every time the gong strikes at the rate of 100 times per

maker supplies -10 volts dc through relay K401 to all

minute, causing the visual signal to flash.

stages of the circuit.

Resistor R311 (not shown) is a trimpot used in the

Resistor R406 (not shown) is a trimpot used in the

circuit to adjust the rate at which the alarm strikes.

circuit to adjust the high-frequency tone. Resistor R408

Clockwise rotation speeds up striking, while

(not shown) is a trimpot used in the circuit to adjust the

counterclockwise rotation reduces it. Normal

low-frequency tone. If adjustment is required, you

adjustment is for 100 strokes per minute. Resistor R302

should always make the low-frequency adjustment first.

(not shown) is a trimpot used in the circuit to adjust the

The normal setting is 500 cycles per second for the low

Figure 7-14.--Block diagram of the unassigned A alarm module.

7-13