Monterey Power Line Signal Analyzer (PLSA) — Instruction Manual

Instruction manual for the Monterey Instruments Power Line Signal Analyzer (PLSA) — a diagnostic meter for complete analysis of X-10® type power line carrier signals, used to identify, measure, and troubleshoot X-10 home automation control signals.

Features

• Identifies all X-10 number and function codes
• Displays signal strengths of all incoming codes using an auto-ranging volt-meter
• Analyzes AC power line noise
• Dissects each X-10 code to examine all bits of the code
• Records in memory up to 190 X-10 codes for later review
• Examines pre-set dim, extended code, and extended data commands

Mode Button Operation

The MODE button on the front panel switches between 5 operating modes. Press the button the prescribed number of times (as shown in the MODE box on the front panel), wait about 1 second, and the PLSA switches to that mode.

Mode 1 — X-10 Signal Identifier & Signal Strength Indicator

When plugged into any 120VAC outlet, the LCD defaults to this mode (press MODE once if not). Any X-10 code received is displayed on the top line with its signal strength (in volts or millivolts) directly underneath; the display shifts left as new codes arrive. The X-10 code consists of 3 characters — the first is the House Code, the next 2 are the Key Code. Example: an X-10 module set to F12 turned ON displays F12 FON with matching signal strengths below.

The signal strength volt-meter auto-ranges from 0 millivolts to 4.1 volts, showing "m" for millivolt readings below 0.1V, and "4.+" if the voltage exceeds 4.1 volts. A calculated threshold (varying 8–25 millivolts depending on line noise) determines whether a code bit registers as binary 1 or 0 — some X-10 devices can still respond to signals weaker than this displayed threshold.

Error Codes (displayed in Mode 1)

• BSC — Bad Start Code: the required Start Code (1110) at the beginning of the first code block is corrupted, often from a noise spike, weak/borderline signal, or two colliding codes.
• BBK — Bad Block: a good Start Code was received but the two 11-cycle code blocks aren't identical, or a true/complement bit pair isn't opposite. Use Mode 3 (Signal Dissect) to pinpoint the corrupted part.
• BCY — Bad Cycle Gap: the silent gap between two different X-10 codes is less than the required 3 complete cycles.
• Lower-case House Code letter (e.g. "f12" instead of "F12"): only one good Start Code and one good Block (of the two identical blocks) were received — common with coupler/repeaters like the Leviton 6201, or when the second Start Code is corrupted.

Mode 2 — Displaying AC Power Line Noise

Press MODE twice. The LCD shows peak noise voltage (frequencies ≥110 kHz) at two windows: at .5ms after zero-crossing (when most X-10 devices sample for a signal) on the top line, and the highest noise between .2ms–.9ms after zero-crossing on the second line. Updated once per second. From field testing, acceptable noise levels are about 15 millivolts ("15m") or less. This mode can also reveal signal strengths of codes too weak to show in Mode 1.

Mode 3 — Dissecting X-10 Codes

While in Mode 1, all 22 cycle signal strengths of the last X-10 code received are stored permanently for review. Press MODE 3 times to dissect the last code cycle-by-cycle, showing the true bit and its complementary bit with signal strengths for each. Cycles 1–2 and 12–13 are the Start Code (1110); cycles 3–6/14–17 form the House Code; cycles 7–11/18–22 form the Key Code. A code chart is printed on the back of the unit for reference.

Coupler/repeater diagnostics: Mode 3 is especially useful for observing signal strength changes after installing a coupler/repeater (e.g. the Leviton 6201 signal amplifier), which receives the first 11-cycle block and amplifies the second.

Modes 4 & 5 — X-10 History Recorder

Records up to 190 incoming X-10 codes in permanent memory, along with signal strength and an offset time (in hours) from when recording began.

• Pressing MODE 5 times resets the History Recorder, clearing all past events and the internal timer, and starts a fresh "RECORDING NOW" session.
• Pressing MODE 4 times continues the current recording session without clearing prior events (used when switching back from another mode).
• If power fails during recording, it resumes on power restoration from where it left off, though the internal timer resets to 00.0.
• Only two Dim or Bright codes in a row are recorded (to conserve memory) if more than two are received consecutively.
• Note: Under noisy AC line conditions, use Mode 1 for more accurate code display — Bad Start Codes (BSC) are commonly recorded when in Modes 4 or 5 under such conditions.

Reviewing Recorded Events

From any mode except Mode 3, press NEXT or BACK on the front panel to display the total number of recorded events (top line) and the last recorded event (bottom line), e.g. "09 CODES RECR'D / #09 JDM 77m 16.3". BACK steps to the previous recorded event, NEXT to the next; hold the button for rapid review.

X-10 Code Transmission Theory

The AC power line crosses zero voltage 120 times/second. X-10 transmissions synchronize to this zero-crossing point: a 120,000 Hz signal burst lasting 1 millisecond represents binary 1; its absence represents binary 0. A complete X-10 code is two identical 11-cycle blocks (22 cycles total) transmitted back-to-back with no gap. Within each 11-cycle block: the first 2 cycles are the Start Code (1110); the next 4 cycles are the House Code; the last 5 cycles are the Key Code. The House/Key Code bits transmit their true bit on the first zero-crossing of a cycle and the complementary (opposite) bit on the alternate half — the Start Code is unique in not following this true/complement relationship.

If the fifth true bit of the Key Code is 0, the first 4 bits represent a Number Code; if 1, they represent a Function Code. Between different code transmissions (block pairs), at least 3 silent power-line cycles must occur — except for Dim/Bright codes (transmitted continuously with no gaps) and Extended Code/Data (no gap between the function code and following data).

Table 1: X-10 Binary Code Equivalents

Pre-Set Dim Commands

Deciphered easily using Signal Dissect Mode. The Pre-Set Dim command contains 5 level bits (32 possible dimming levels). Format: House Code (L1 L2 L3 L4) | Key Code (1 0 1 L5 1) — L5 is the MSB, L1 the LSB, ranging from full ON (11111) to full OFF (00000). Example: X-10 codes B7 then EPD show a light set to B7 accepting the Pre-Set Dim command; House Code E = 0001, and if L5=0, the level bits equal decimal 8 (25% dim, 8/32).

Extended Code & Extended Data Commands

The X-10 format allows additional data/code to be sent after an Extended Data or Extended Code command with no cycle gap. The PLSA can record up to 7 bytes (56 cycles) of extended code/data for later review, viewed in true bit/complement bit form. Dissecting the signal (Mode 3) after an Extended command shows only the additional code/data, not the command itself.

Maintenance

If the PLSA is connected to a voltage source greater than 130 volts AC, an internal fuse will blow — disconnect power and replace with a type 2AG, 1/2 Amp fuse. An internal LCD contrast adjustment is also provided; be careful not to touch any bare leads inside while adjusting contrast with the power on.

Monterey Instruments, a Division of Monterey Pool Products — Oceanside, CA, (760) 941-3666.