Specifications

Alto 818 Installation and Operation
2-24 P/N 66109074001 Rev. D
2.7 ANALOG PROXIMITY SENSORS
As indicated in Table 2-1, the Alto 818 can accommodate various analog proximity readers.
These sensors are described below.
2.7.1 PROXIMITY SENSOR OPERATION
The Alto 818 ACU generates low level RF in the range of 2 to 27 MHz. This frequency range is
swept from high to low and applied to the reader ports. When an analog proximity sensor is
connected to one of the sensor ports via a coax cable, the sensor will emit a low power RF field
from its surface which is concentrated in a region the distance of which depends upon the read
range of the reader.
When a command key is placed in the region of this RF field, L/C tank circuits in the key will
modulate the RF field emitted by the reader. The precise frequency of this modulated signal is
a function of the tank circuits in each key. The key reader circuitry in the Alto 818 has the ability
to detect this key-specific frequency and thereby to discriminate between key codes. The ACU
then makes an access decision based on database parameters for each door and key code.
2.7.2 PROXIMITY SENSOR MODELS
The SE 28XX sensors consist of a loop antenna and a solid state electronics package mounted
in a Lexan enclosure. They can be either surface-mounted or concealed in a wall. The reading
ability of these readers is equal on both sides and is not affected by common construction
materials, except metals. These sensors are 7.5 inches (19.1 cm) square, 0.67 inches (1.7 cm)
deep.
SE 2814/15 PROXIMITY SENSORS
The SE 2814 sensor and the SE 2815 sensor have a read range of 2 to 4 inches (5 to 10 cm).
These two sensors differ only in that the SE 2814 has the coax connector located on the rear for
surface mounting using the SE 2700 standoff, and the SE 2815 has the coax connector located
on the edge for recessed mounting.