Figure 3-8.--Type IC/E1D1 electronic signal unit.

to the dropout range and relays 1V, 2V, and 3V drop

out. Contact 1Val opens, disconnecting relay SE.

After a time delay of 0.3 to 0.5 seconds, relay SE

opens, closing its SEb1 and SEb2 contacts and

energizing relay 4V from the emergency source.

When contact 4Val closes, it connects the emergency

source to coil TS of the transfer switch, which, in turn,

operates, transferring the load to the emergency

source.

After a short delay, contacts TSa4 and TSa5 open,

disconnecting coil TS from its operating circuit.

However, TS is now being held in the operated

condition mechanically. This completes the transfer to

the emergency supply.

Upon restoration of the normal power to the

selected range, the retransfer is begun by the

energizing of relays 1V, 2V, and 3V, which close,

energizing relay SE. Contacts SEb1 and SEb2 now

open, disconnecting relay 4V from the emergency

Figure 3-8.--Type IC/E1D1 electronic signal unit.

source. After the time delay, relay 4V opens, closing

its 4Vb1 contact and completing the normal supply

circuit to the transfer switch coil, TS, which again

The POWER ON light, a backlighted push button,

operates, transferring the load back to the normal

tests the audible signal of the unit. The SILENCE

supply.

RESET push button silences the alarm (the red flag

When you put the ABT in the manual mode, you

will not reset until power is restored to the bus) and

no longer have the automatic transfer capability. You

resets the unit when power is restored to the bus.

may select either the normal or emergency source of

There is usually a bus failure alarm unit for each

power by putting the manual switch in the position

bus associated with the switchboard.

desired.

FUSES AND FUSE HOLDERS.-- The basic

The test switch is used to test the ABT for its

type of fuse used in the IC switchboard is designated

automatic transfer capability. The control disconnect

F03 plastic or ceramic with silver-plated ferrules.

switch must be in the AUTO position when using the

test switch.

The fuse holders used in IC switchboards are the

SWITCHES.-- The types of switches usually

dead-front blown fuse indicating type. The two basic

found on IC switchboards are the JR, JL, toggle, and

types of fuse holders used with the F03 fuses are the

rotary snap switches. These switches were discussed

FHL10U and the FHL11U.

in chapter 2 of this manual.

LAMPS AND LAMP HOLDERS.-- Both neon

BUS FAILURE ALARM UNIT.-- The type

and incandescent lamps are used in the IC

IC/E1D1 electronic signal unit (fig. 3-8) is designed

switchboard. Neon lamps are used as synchro

as a bus failure alarm. The unit contains an electronic

overload and blown fuse indicators, and incandescent

solid-state oscillator, which drives a 2-inch howler

lamps are used for power indication.

unit that provides an audible signal upon loss of power

Incandescent lamp holders are normally rated at

on the supervised bus. A red drop flag installed on the

unit provides a visual signal upon loss of power.

120 volts. These lamp holders use step-down

transformers for ac applications or resistors for dc

A small nickel-cadmium battery provides power

applications to permit use of a lower voltage rated

for the oscillator. The battery is maintained on a low

lamp, Lamps that are rated at 120 volts are not suitable

charge when the supervised bus is energized. The unit

for the vibration and shock conditions encountered

will operate on 115 volts, dc or ac, and 60 or 400 hertz

aboard ship.

without modification.

3-10