Cal. Code Regs. tit. 21 § 1701.1
The compatibility specifications for automatic vehicle identification (AVI) equipment in Articles 2 through 5 have been developed around two principal components, a reader and a transponder. The minimum role of the reader is to:
A half-duplex communications system is envisioned where the transponder takes its cues from the reader. The specification is meant to define a standard two way communications protocol and to further define an initial set of data records. A summary of the key compatibility specifications found in Articles 2 through 5 are set forth below:
| Reader Specifications: | |
| Reader Trigger Signal | 33 microseconds of unmodulated RF |
| Reader Send Mode (Downlink) | |
| Carrier Frequency: | 915 ± 13 MHz (subject to FCC assignment) |
| Carrier Modulation: | Unipolar ASK (Manchester Encoded) |
| Data Bit Rate: | 300 kbps |
| Reader Specifications: | |
| No. Data Bits: | Application Specific |
| Field Strength at Transponder Antenna: | 500 mV/m (minimum) |
| Transponder Specifications: | |
| Technology Type: | Modulated Backscatter |
| Transponder Antenna Polarization: | Horizontal |
| Field-of-View: | Operation within 90° conical angle |
| Location: | Front of Vehicle |
| Transponder Send Mode (Uplink) | |
| Carrier Frequency: | Same as Reader Send Mode |
| Carrier Modulation: | Subcarrier AM |
| Subcarrier Modulation: | FSK |
| Subcarrier Frequencies: | 600 kHz ± 10% and 1200 kHz ± 10% |
| Data Bit Rate: | 300 kbps |
| No. Data Bits: | Application Specific |
| Receiver Field-Strength | |
| Threshold: | 500 mV/m ± 50 mV/m (minimum) |
NOTE: All mV/m specifications are in RMS voltage.
Cal. Code Regs. Tit. 21, § 1701.1
Note: Authority cited: Section 27565, Streets and Highways Code. Reference: Sections 27564 and 27565, Streets and Highways Code.