Integrator and Lamp Driver

TM 11-582695-35

direct proportion to the signal level at the base, and is

transformer T1 which provides a voltage gain of two.

filtered by C17. Resistor R39 provides a minimum

The +12 volt supply voltage is connected to transistor

voltage across C17. This reduces the time required for

Q1 through voltage dropping resistor R27 which is

input pulses to fully charge C17. Resistor R40 is

bypassed by capacitor C8. Capacitor C9 is a high

variable so that the dc input level to the reference input

frequency bypass that provides signal ground for the

of Al can be adjusted.

tuned circuit. Resistors R24 and R25 in the emitter

circuit of transistor Q1 provide dc bias. Resistor R25 is

Slicer A1 Slicer A1 is an integrated circuit

bypassed for ac by capacitor C12. Since resistor R24 is

not bypassed, it provides a small amount of signal (ac)

(fig. 5-24). Capacitors C18 and C19 provide supply

feedback. Resistor R23 is an impedance match for the

voltage decoupling. The -6 volts through resistor R41

secondary of transformer T1 because the input

speed up transitions from logic one to logic zero. When

impedance of Q1 is high. Resistor R33 at the secondary

the input signal (pin 3) is more positive than the

side of transformer T2 has the same function. Cable

reference voltage (pin 2), the output is low (logic zero);

traffic alarm signal XCPCM is taken from the secondary

when the input signal is negative with respect to the

of T1 and sent to alarm monitor 1A12A6.

reference voltage, the output is high, (logic one).

Resistor R46 is an isolating resistor to protect T1 and

Q1 in the event of a malfunction in the external circuit.

Integrator and Lamp Driver. The integrator

(transistor Q9) is an emitter follower. Resistors R42 and

(2) Amplifier Q2 is a grounded emitter

R43 and capacitor C20 determined the base emitter

amplifier with a voltage gain of approximately 35. The

bias. Pulses of 1CSPCM charge capacitor C20 and

input signal to this amplifier is direct coupled from

maintain a positive dc voltage as long as signal

transistor Q1. Resistor R28 is the collector load resistor

1CSPCM is active. The output voltage is coupled

and resistor R29, R30, and R31 provide dc bias.

through current limiting resistor R44 and keeps

Resistors R30 and R31 are bypassed for ac by

transistor Q10 (which acts as a switch) turned on. Lamp

capacitors C11 and C13. Resistor R29 is not bypassed

DS1 then remains lighted as long as 1CSPCM activity

and provides a small amount of signal feedback. Dc

continues. If the pcm signal fails, Q9 turns off, capacitor

feedback from the junction of resistors R30 and R31 to

C20 discharges through R43 and Q10 turns off. Output

the base of transistor Q2 provides temperature

signal 1CRFAIL is then logic one and lamp DS1 is off.

compensation between transistors Q1 and Q2.

When transistor Q10 turns off, lamp DS1 receives a

small current to keep it warm through R45. Since a

(3) Amplifier Q3 is an emitter follower

warm lamp has a higher resistance than a cold lamp,

which couples the output signal of transistor Q2 to the

when Q10 turns on, the current surge is not as great.

primary windings of transformer T2 with minimum

loading on transistor Q2. Resistor R32 is the emitter

Voltage Filtering Components, Synchronous

load resistor. The ac signal is coupled to transformer T2

Mode (1A12A2).

Voltage filtering components L9

through capacitor C14. Transformer T2 provides a

through L11 and C21 through C25 limit the coupling of

voltage gain of four.

switching transients and other stray signals to the power

circuits.

(4) Dual transistor circuit Q5 contains a

common emitter amplifier Q5A and a temperature

Voltage

Filtering

Components,

compensating bias network consisting of QSB, resistor

Asynchronous Mode (1A12A13).

Voltage filtering

R34 and bypass capacitor C15. This type of biasing

components L13 and C26, C27, and C30 (for the +5 vdc

results in a linear output which is direct coupled to the

supply voltage) and L15, L16 and C29, C33, and C34

input (pin 2) of slicer Al. Resistor R35 functions as the

(for the +6 vdc supply voltage) limit coupling of

collector load resistor. Resistor R36 provides dc bias

switching transients and other signals to the power

and is bypassed for ac by capacitor C16.

circuits. The +12 vdc supply voltage is filtered at the

input by L1 and C1, voltage regulated by R1 and CR1

(5) Amplifiers Q7 and Q8 are a pnp-npn

and filtered by C2. It is then distributed to various

common-collector complementary pair designed to

circuits through decoupling circuits as follows:

eliminate temperature drifting effects. Resistors R37

through L2 and C3 and C4 to integrated circuit A4 and

and R40 are the emitter load resistors. Resistor R38 is

transistors Q1 and Q2; 2. through L8 and C25 to

a current limiting resistor to protect Q8 against current

transistor Q4; 3. through L3 and C8 to integrated circuit

surges, at turn on time or any time when C17 is

Al; 4. through L14 and C28 to integrated circuit A3.

discharged. The signal at the base of Q8 is rectified by

the base emitter junction to provide a dc reference in

2-80 Change 1