Periscopes and Support Sights.

(c) The select levers permit either manual or power operation of the

turret.

(d) The handwheels enable manual operation of the turret by the gunner.

(e) The gunner's control handles enable electric power operation of the

turret by the gunner.

(f) The drive system enables the commander to override the gunner's

control of the turret.

(6) Periscopes and Support Sights.

(a) There are eight periscopes for daylight viewing in all directions by

the commander.

(b) There are two periscopes for daylight viewing by the gunner to the

right and the left of the main sight.

(c) Blackout covers are provided for the periscopes.

Closed blackout

covers prevent the interior light from being seen from the outside.

(d) The front ring sight is used when aiming and firing at a low-flying

aircraft. It is also used as an emergency sight for ground targets.

(e) The vane sight is used by the commander to quickly align the turret

with the target.

b. Location and Description of Major Components.

(1) Radio Antennas. Two antenna mounts are on the turret. One is to the

right of the commander's hatch cover and the other is at the rear, on the center

line of the turret.

(2) Periscopes.

Seven wide-vision M17 periscopes and one M27 periscope

allow 360ƒ vision at the commander's station.

These periscopes have blackout

covers. The gunner has two periscopes with blackout covers.

(3) Ring Sight.

The ring sight is mounted on the outside of the turret.

It is used to track flying targets and also as backup for the ISU. The eyepiece

aligns the ring sight on the target and a thumbscrew adjusts the eyepiece.

The

ring sight tracks with the 25mm gun.

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