Use of Pan-Tilt device is the easiest way of increasing field of view of a camera.

They ensure, together with manual or computerized control and "motozoom" type of lens, accurate tracking of relevant event. A fixed camera is always watching specified area and its position not always allows to spot details of the observed image. If we install the camera on Pan-Tilt device and additionally equip it with "motozoom" type of lens, we will have the opportunity to control large field of view and to perform track on the selected object.

Each Pan-Tilt device has its load capacity, which cannot be exceeded, therefore it should fit the weight of the camera.

Another parameter is rotation speed. An average value is 10 degrees per second for simple devices, however there are also Pan-Tilt devices with speed from 0.1 to 400⁰ per second. This parameter is especially important e.g. for event registration in stadiums, where system reaction time may decide about the sense of employing Pan-Tilt devices.

Very important feature of Pan-Tilt equipment is positioning repeatability, the feature that is very hard to achieve in cheaper devices. In good class devices the error is not higher than 0.2⁰

Like housings, Pan-Tilt devices should also have given IP class.

We distinguish two basic groups of Pan-Tilt devices:

• Working in one plane, usually horizontal. Each Pan-Tilt device of this type allows the camera to be set in initial vertical position. Horizontal rotation is limited in simple devices to 350⁰. Professional versions have ability of full rotation. Devices of this type are sometimes called scanners.
• Working in two planes, vertical and horizontal. Vertical rotation is usually limited to 90⁰. These devices are reasonably called Pan-Tilt mechanisms.
Rotation of the device in horizontal plane is commonly called "pan", and in vertical plane - "tilt".

These devices can be also divided into two groups:

• Pan-Tilt devices with camera mounting base placed on the top. They also allow IR illuminators to be installed. They don't permit the camera to be significantly tilted down for the reason of mechanical construction.
• Pan-Tilt devices with camera mounting base placed alongside, their characteristic feature is wide vertical angle. Unfortunately, installation of IR illuminators is quite difficult with them.

Control of Pan-Tilt devices and motozoom lenses requires employing additional equipment - drivers and telemetry receivers.

The driver (controller) is a device equipped with micro-controller that allows, depending on the version, to control from 1 to even a few hundreds of Pan-Tilt sets.

In the case of a single camera, we can use simple controller based on relay systems.

Nowadays, integrated speed dome cameras are increasingly used.
If we decide on that solution we should choose a device of name-brand company. Although camera modules can be comparable, the rotating mechanism is critical for the general performance. Every rotating mechanism consists of mechanical parts which wear out. In cheap devices the cogwheels are made of plastic and - especially when the camera is intensively exploited, its lifetime is considerably reduced. We should be aware that durable mechanism must cost a little and choose proven models of speed dome cameras.

Speed dome camera is usually controlled with a special console. The device is also available in several versions:

• simple (cheap) - where control is performed with the use of buttons - this kind is not comfortable nor suitable in case of frequent operation
• consoles equipped with joystick - significantly enhancing control
• advanced keyboards - with LCD displays, abilities to control other devices e.g. recorders, matrix, etc.

To control professional cameras some specific protocols are used. Most of them are implemented in recorder firmware, as well as in adequate software - in the systems based on cards, e.g. GeoVision. They give opportunity of remote control without use of expensive specialized keyboards.

Pan-Tilt devices in digital networks.
Increasingly popular use of digital transmission in surveillance systems also requires to employ adequate Pan-Tilt devices. An example of the camera integrated with Pan-Tilt mechanism, adapted for work in these networks is e.g. one of products of ACTi Corporation. The CAM-6621 Video Network Camera is characterized by 23x optical zoom and full remote control through network - thanks to built-in network module. Besides TCP/IP output, it has also standard video signal output and bidirectional audio transmission.

PTZ IP camera ACTI CAM-6621

When designing an installation, we should consider the fact that covering the whole monitored area with fixed cameras provides reliable and more efficient observation. Supplement of the system, in the form of high quality Pan-Tilt camera with zoom lens, helps to increase capabilities of the system for observation of small details. However, we have to remember that zooming in on an object, without fixed camera monitoring, means that we can't observe wider area at the same time.