CED 3505 Programmable attenuator

The CED 3505 and 3505HP are single-channel programmable attenuators offering main attenuations from 0dB to over 100dB in 2.5, 3 or 5dB steps. Other attenuation ranges are available to special order.

Control of the attenuation and other programmable features of the 3505 is via an internal USB-serial port. It may be controlled by scripts in Spike2 or Signal. Fast attenuation changes may also be implemented via a parallel port designed to interface with a CED1401 digital output. In this way, the sequencer facility in the CED Spike2 software package can control the attenuation for real-time synchronisation under experimental conditions.

The standard 3505 has an additional output connector producing an “attenuation changed” pulse. In the 3505HP model, this connector is replaced by a 6.3mm stereo jack socket. The jack socket carries the output from an internal audiometric headphone amplifier, designed to drive standard audiometric headphones to sound pressure levels of around 140dB. The attenuator output signal can be routed to one or both headphones, and there is an independent calibration attenuator for each headphone channel.

Box size: 240mm x 240mm x 46mm (W x D x H), external mains-driven power supply.

Owner's Handbook





Cambridge Electronic Design Limited

Registered in England: 972132

Registered office:

  • Cambridge Electronic Design Limited,
  • Technical Centre,
  • 139 Cambridge Road,
  • Milton,
  • Cambridge CB24 6AZ

VAT: GB 214 2617 96

Producer Registration number: WEE/BD0050TZ

Terms and Conditions of Sale

For our US customers, we can provide tax form W-8BEN, that identifies us as a UK company.

DUNS: 219151016
NAICS: 423490
Commodity codes
Hardware: 84716070
Software: 85234945

By email:


By post:
  • Cambridge Electronic Design Limited,
  • Technical Centre,
  • 139 Cambridge Road,
  • Milton,
  • Cambridge CB24 6AZ
By telephone:

(Int.+44) (0)1223 420186

From North America (Toll Free):

1 800 345 7794


Privacy policy

CED, through this site, does two things that relate to privacy. We would like to explain them.

Emails from down-loads

We offer free down-loads of many files on our site, from test programs to complete install files for updated versions of major packages like Spike2 and Signal.

When customers wish to take a down-load of a major package, we ask a few questions, including their name, email address, the serial number of the software for which they seek an upgrade and whether they would like an automatic email whenever we update the product. This information is emailed back to CED when they access the final down-load screen. Within this email, your browser transmits the type and version of browser you are using, and the screen resolution you are running.

The reasons why we take and keep this information are that it is useful for our software development team to know who has taken the latest versions, and it is useful for our web site development team to know which browsers people are using to view our site, and what resolution they have their screens set to.


When people down-load a major package, we try to write a cookie, a small file in your computer, that records your name, serial number of the software package, and the version you are down-loading. These files have a lifetime of one year.

The reasons for storing this information are firstly that if you ask for another down-load some other time, your details are read from the cookie and are pre-written into the form, to save you looking them up again. The other reason is that next time you access our site, your browser looks through your CED cookies and compares the versions down-loaded with the latest version numbers read from our site. If there is a later version of a product you have already down-loaded, we tell you on the home page screen, so you know that it is worth going to the down-load page again.

None of this information is ever given to anyone outside CED. ×