8A1. Types of circuits. (See Figure 8-1.) All
electrical circuits that connect to the underwater log are known as Y circuits. All underwater logs, regardless of the manufacturer or
type have circuits as follows:
1Y - Speed transmission circuit|
2Y - Distance transmission circuit
3Y -Constant frequency supply
2Y100 - Distance transmission to dead
8A2. 1Y circuit. (See Figure 8-1.) The speed
pointer shaft of the master speed indicator
drives the transmitter motor for the 1Y circuit. The movement of the pointer shaft positions the rotor of the transmitter in a corresponding angle, and thus positions the repeater motor which rotates to the same angle.
The R1 and R3 internal connections in the
speed and distance indicator speed repeater
are reversed because the transmitter is actually rotated in a reverse direction to the
pointer in the master speed indicator. The
transmitter also feeds into the speed corrector
in the gyrocompass, and the speed input in
the torpedo data computer.
8A3. 2Y circuit. (See Figure 8-1.) The 2Y
circuit is the basic circuit in the Pitometer
log, as rotary distance is first obtained in the
rotary distance transmitter and is later
changed to a speed indication in the master
The 2Y circuit supplies 110-115 volts a.c.
to the distance transmitting motor in the rotary distance transmitter, and its associated
repeating motors, one of which is in the
master speed indicator, and one in the speed
and distance indicator. The circuit from the
rotary distance transmitter to the speed and
distance indicator passes through the repeater
switch on the A.C.O. board. In addition, this
circuit supplies power to the pump drive
motor (through the transtat, armature rectifiers, and field rectifiers). Connection to
the motor circuit is made through two jumpers to terminals 2Y1 and 2YY1.
8A4. 3Y circuit. (See Figure 8-1.) The 115 volt 60 cycle a.c. supply driving the synchronous motor in the master speed indicator is
the 3Y circuit. As the entire speed calibration
of the log depends on the operation of this
motor at constant speed, the 3Y frequency
must be held to 60 cycles. To permit the
operation of the log if the constant frequency
control unit should fail, a selective switch is
usually provided that permits the 3Y circuit
to operate from the ship's a.c. supply. On
some of the latest submarines the ship's a.c.
supply is considered accurate enough, and
no constant frequency control unit is provided.
8A5. 2Y100 circuit. The right-hand self-synchronous motor in the rotary distance
transmitter transmits rotary distance at the
rate of 360 revolutions per mile into the 2Y100
circuit. This is connected only to the distance input repeater motor in the dead reckoning analyzer, and not to the tracer of the
tracking table. This circuit switch is generally located on the gyro control board, rather
than on the I. C. board.