56K Dialup Modem Communication Troubleshooting Guide: no handshaking

Possible Issues:

1. Display or Modem Card not getting power.
2. Phone lines got damaged going out to the display.
3. Wrong phone number.
4. Modem card at display has failed (can be located inside display next to the controller or in a communication box at the base of the sign.)
5. If installed, potentially could have a bad phone line surge protector.
6. Display quick connect phone line not connected to J6.
7. If MDC display and V15 Config crashes when trying to connect, check cable to J6, if in any other port it crash's V15 Config. May need to power cycle display too.

Pictures & Literature

Modem Installation Quick Guide: ED14556_Rev 1.pdf

Modem Communication manual: ED14744_Rev 1.pdf

Troubleshooting

1. Verify the display has power.

   If the display is showing content or has a heartbeat (pixel blinking on the lower right side of the display), then display has power.

   1. If the display is blank, cycle power to the display (i.e. flip breaker off for 40-60 seconds and flip back on), and verify the display goes through a start up sequence; if no boot up, then there is likely a power issue. 
2. Verify the correct phone number is being dialed for the sign.  If correct, try dialing from another phone if possible and see if handshake is heard.
3. If the display does have power and the correct phone number is being used,  the local phone company can be contacted for checking the phone lines.
   1. Depending on ease of access to the modem card, determine whether it's best to call the phone company first (i.e. if the modem card is inside the display and a lift is required to access the display, it is advisable to first have the phone company check the lines). 
   2. Check for proper operation of customer's internal or external 56K V.90/V.92 modem.

1. Check the diagnostic LEDs on the modem card (see above picture.)
   1. The green power light should always be on; should have approximately 10 - 11 V DC (Picture Above shows AC Voltage) into the modem card.
2. Measure the voltage of the phone line (Tip and Ring) when it is not ringing. Voltage should be about -48V DC (tip is positive grounded).
   1. If TB2 hardwire connection is being utilized on the modem card, then the voltage can be measured there with the volt meter's positive lead going to tip (left terminal) and negative lead going to ring (right terminal), assuming modem card is oriented so that the column of diagnostics LEDs are on the left side. 
   2. If a positive 48 VDC is measured, then the wires need to be swapped.
3. Can try measuring ring voltage; will want to be careful when measuring as you will get a shock if wires are touched while it's ringing.
   1. Try dialing into the display and while it's ringing, measure the ringing voltage. Should be roughly 90V AC.
   2. When making a call, the 90 V AC (~20 Hz) is superimposed over the DC voltage, meaning that a voltmeter/multi-meter will act really funky for a lack of a better term when trying to take measurements (basically just verify the voltage measurements are jumping around when trying to measure.)
   3. If a connection is made the voltage between tip and ring should measure ~ -7 VDC.
      1. The red carrier detect diagnostic LED should also come on if the modem makes a connection with another device. 
4. Try attaching an analog phone out at the modem at the sign. Phone can be connected to J5 on the modem PCB with a standard phone cable (if using a butt set, may need stripped wires and use alligator clips if phone wires going to display are not terminated with RJ11 jack. By "standard phone cable" it is assumed straight-through wiring as that has what's worked for us before however we can't guarantee that will always be the case.)
   1. Call the number for the display from an outside line (cell phone or other) and see if the phone connected to J5 rings.
   2. If the analog phone does not ring, try making a call out from the analog phone to a phone/cell with caller ID.
      1. If the other phone/cell rings, check the number coming in and verify this is the same number being used to dial the display.
      2. If the phone/cell rings and shows the correct number and everything else has been checked, likely the modem card has gone bad.