No output from the internal speaker.

First of all make sure the Tone Ringer is turned "on" at the switch on it's front panel and that the volume control is turned at least half-way to maximum loudness.

If it's a new installation:

Incompatibility with the host system or telephone is the usual cause that a newly installed Tone Ringer will not work at all. Follow this procedure before you do any further tests to see if you are triggering the tone ringer with a "standard" ring-signal. If your analogue test telephone will not ring the Tone Ringer is never going to work in your application. If the analogue test set worked OK, make sure that J1 is set to "Internal". If J1 is correctly set, make sure the internal speaker is plugged into J3. If these tests do not isolate the problem, it's likely that the Tone ringer will need replacing.

If it's a previously OK Tone Ringer has suddenly stopped working:

First check that the tone ringer is switched "on" and that the volume control is turned up. If you are unsure if a ring-signal is being received, follow this procedure before you do any other testing. If the analogue test set worked OK, double-check that J1 is set to "Internal" and that the internal speaker is plugged into J3 (in case someone has been "playing" with the unit). If these tests do not isolate the problem, it's likely that the Tone ringer will need replacing.