The instrument consists of a sighting arm with a threaded collar at one end for attaching to tripod. A clamping screw is fitted to hold the collar securely in the required position. The collar supports a fork, into which a mirror is pivotted. The mirror has a small unsilvered spot at its centre and provision is made for fine horizontal adjustment by means of a milled knob. A rod is hinged to the upper edge of the mirror and this passes into a female screw tube to allow for adjustment of its length. The tube is hinged to a lever at its lower end, which forms a Morse key. The lever is hinged to the stem of the instrument and is held against a fixed stop by a spring attached to the collar. A milled disc, fixed near the lower end of the tube, is for tilting the mirror as may be required for signalling. A socket, with clamping screw, is provided at the forward end of the sighting arm to house a supplementary mirror, or the sighting vane extension arm.
The supplementary mirror is pivotted in a forked frame, and has a spigot which fits into the socket at the end of the sighting arm. At the centre of the mirror, a piece of paper is pasted, which has the same form as the sighting vane. The sighting vane extension arm is a three-piece hinged rod. at the forward end is a spring-loaded, hinged sighting vane, and a circular sight with crossed metal strips.
Tripod: Three wooden legs with brass cappings at the upper ends, hinged to the brass tripod head which is threaded for insertion into heliograph collar. A brass cap, with retaining chain is provided to protect the tripod head when not in use. The lower points of the legs are set to an angle of 60 degs and are shod on the inside surface with steel plates. Two brass loops are provided to accommodate a carrying strap. O.A. Height 39.7" (100.8cm)