The CED 3505 and 3505HP are single-channel programmable attenuators offering main attenuations from 0dB to over 100 dB in 2.5, 3, or 5 dB 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 6.3 mm 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 140 dB. 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: 240 mm × 240 mm × 46 mm (W × D × H), external mains-driven power supply.

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