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Knowledge Base > Discontinued Products > 528E Voice Processor

Where can I find a schematic for the 528E Voice Processor?

In order to choose the correct schematic for your particular 528E unit, you will need to derive both the unit revision and the manufactured date from the serial number of the unit. This number always begins with the number “80”, and will be on a sticker on the bottom of the 528E.

Depending on the age of the unit, this number could appear in a couple of possible formats. This is a key detail, as schematics are not available for current serial numbers.

Current Serial Numbers:
Current units have serial numbers in the following format:

120V version: 80-4528EANA0912176
230V version:  80-4528EAEU0912176

The presence of a hyphen and either “NA” or “EU” in the serial number are both indicators that this is a current serial number.

If you need repairs for current serial numbers, please contact Symetrix Support at

Old Serial Numbers:
Older units have serial numbers that appear without a hyphen, and will have the manufacture date printed on the sticker.

Example: 800528E0B0854

The unit revision is shown by the two characters following the model number (800528E). In the example above, the “0B” points to a Revision B unit.

The manufacture date for older units can appear in a couple of different date formats. One may see a more typical date format (e.g. 09/19/05), or perhaps a format as shown in the picture below. In this example, the year is first – so the manufacture date is May 7, 2008.


Once the unit revision and manufacture date have been established, download the relevant schematic from among the links below.

528E_A00 (1995) Schematic
528E_D1 (1996) Schematic
528E_D02 (1996) Schematic
528E_D03 (1996) Schematic
528E_B00 (1997) Schematic
528E_B01 (1998) Schematic
528E_1C00 (1999) Schematic
528E_1D01 (2002) Schematic
528E_1D02 (2007) Schematic

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