Frequently asked Questions

Farfisa Intercoms 



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question-answerCan I run my intercom cable together with 220 VAC or 24 VAC or 12 VAC?

DEFINITELY NOT. any current on these lines will interfere with the quality of the intercom system. a 50 Hertz HUM will be heard on the audio (buzzing sound)


question-answerwhat Electric locks can I use with Farfisa Intercoms?

There are many types of electric locks, Your first concern is the voltage and the current that the lock requires.Most electric locks work on 12Volts AC or DC. the prefered is AC as the lock will buzz when the voltage is applied. the buzzing sound notifies the visitor that the gate is being opened. the most commonly used electric locks are strike locks (12AC ??100MA and CISA locks (12VAC ?? 2A) CISA Electric locks are strong and robust, designed for outdoor applications. To ensure proper performance, use a separate 2 amp transformer and 1471 relay installed as close as possible to the lock. Strike lock are mainly used for internal doors and can be operated directly from the farfisa 12VACsupply up to 50 meters on 1mm cable

question-answerVideo Transmission, long distances, what Type of cable should I use?

Military spec RG-59 Coax you can run up to 300 meters without amplification, greater distances can be achieved with larger coax (RG-11) and video amplification

question-answerVideo Transmission, can I use 75 Ohm coaxial cable?

YES, with military spec RG-59 coaxial cable, you can run up to 300 meters with out amplification, greater distances can be acheived with larger Coax (RG-11)   and video amplification

question-answerCan I use twisted pair  telephone cable?

YES, ensure that it is proper non shielded twisted pair telephone cable, the maximum distance is 200 meters, for long driveways, it is recommended that you use 75 ohm Coax from the gate to the central DB in the building. from there you can wire to the intercoms with twisted pair



question-answerDo 1/3″ cameras need a 1/3″ format lens and 1/2″ cameras need a 1/2″ format lens?

Yes. However, you can also use larger format lenses on smaller CCD cameras. Example: A 1/3″ camera will take a 1/2″ or 2/3″ format lens. A 1/2″ camera will also take a 2/3″ format lens.

question-answerSince the same plug is used for video and DC auto iris lenses, will the camera determine which type of lens is connected?

There is a switch selector labelled DC-AI (or similar). Select the switch that matches the type of lens installed.


question-answerWhat are the common sizes of CCD image sensor in CCTV cameras?

The most common sizes are 1/3″ and 1/2″ sensors.


question-answerWhat does the F/ number represent in the lens specifications?

The F/ number represents Aperture Ratio. It tells you a ratio between the maximum and minimum iris opening. Auto Iris lenses adjust according to changing light conditions.


question-answerWhat does the focal length (in millimeters) determine?

The focal length determines what you will see on the monitor. This is called Field of View and is expressed in degrees. Example: A 4mm 1/3″ lens will give you a 63?? of horizontal field of view; an 8mm 1/3″ lens will give you 34?? field of view.


question-answerWhat Is a Balun?

A Balun is an impedance matching device that converts  between balanced and unbalanced signals. It matches the impedanceof 75 Ohm coax   to 120 Ohm of twisted pair. the Balun also helps to minimise losses, attentuation and introduces a high level of common mode rejection which is necessary for reducing for   reducing noise.

question-answerWhat is a DC or DD auto iris lens?

DC or DD (direct drive) lens funtions the same as a video auto iris lens with the exception that there is no amplifier built into the lens. The amplifier is built into the camera. The light dependant varying voltage will open and close the iris.


question-answerWhat is Vari-focal lens?

Vari-focal lenses have the ability to change focal length  similar to a zoom lens, However there ia a major differences between the 2. Most vari-focals are compact in size and do not have the ability to track (maintain focus while changing focal length.

question-answerwhat is a video auto iris lans?

A Video Auto Iris lens has a little amplifier built in which responds to the amount of ambient light and will open or close the iris automatically to maintain the same amount of light coming into the CCD imager. This allows the picture to not become too bright or too dark.

question-answerWhat is a zoom lens?

Zoom lenses have the ability to change focal lengths much like a vari-focal. However, they differ in many ways from a vari-focal. A zoom lens typically offers a wider range of focal lengths and is physically larger than vari-focal. They can be purchased in Manual, 3-motor type, and Auto-Iris versions. They also have the ability to track (maintain focus while changing focal lengths) and can be operated remotely. Some motorized zoom lenses also offer a Pre-Set ability for the zoom, focus, and iris functions.

question-answerWhat is ICR Function

ICR function for Day/Night switching  (ICR = IR Cut Filter mechanically removable) Through the use of the ICR function a real* Day/Night functionality of the camera can be realised. Using a so-called filter shifter, the IR Cut Filter can be swivelled in, which means that in day mode the IR Cut Filter is moved in front of the sensor in order to block out the interfering infrared light. In night mode the IR Cut Filter is moved away so that IR light may pass through.

question-answerWhat is the advantage in using a DC Auto Iris lens?

DC Auto Iris lenses generally cost less since they do not have an amplifier, only driving coils for iris.


question-answerWhat is the function of the lens iris?

The iris is the mechanism which allows more or less light into the lens by the opening and closing of the iris leaves.


question-answerWhen do you use a BALUN?

A balun is needed when running a video signal over twisted pair cable. The balun is connected between the coax cable and the twisted pair to match the impedance of the transmission lines.

question-answerWhere does the Auto Iris lens get its power from?

Power for the Auto Iris lens comes from the camera. The 4-pin plug, in most cases, is a small rectangular connector that plugs into the back or side of the camera.