CDM1550LS+ PA System Wiring?

[kf6ywx]

I have a CDM1550LS+ connected to a Federal Signal PA300 so as to use a common mic between the PA system and the radio. I've got the switch that triggers PA mode firing a DPDT relay which simultaneously shorts pins 14 (PA switch) and 7 (ground) on the radio, and acts as the PTT switch on the "mic" that would be on the PA300. I've then got pins 1 and 16 (external speaker) wired to an isolation transformer, then into the PA300 on the mic lines.

When I throw the switch into PA mode, I'm unable to use siren tones and the airhorn, as expected. When I key the mic, the display on the radio reads "Public Address". However, instead of mic audio, I'm getting the radio traffic through the PA system, even while I've got the mic keyed.

I'm guessing this is in the programming somewhere, but I'm confused as I have the "Accesory Pins" tab selected and used the default settings from the pulldown list for "Public Address" which assigns pin 14 to the PA switch and pin 4 to External Alarm.

Anybody know why I'm getting the radio traffic instead of the mic audio? Thanks. -Chris

[wavetar]

I've never used the PA feature before, so excuse my ignorance. Is the radio supposed to put the mic audio onto the external speaker outputs in PA mode?

[kf6ywx]

That's what the help file reports. And it's language (hopefully intentional) is specific. It says "...radio mic audio...to THE external speaker...." instead of something vague like "...AN external speaker...", so I can only assume that they are reffering to the external speaker at pins 1 and 16. I have a local dealer friend who also thinks it is programming, but I am just trying to ask around and be sure. Five or so minds is better than two, no? Thanks. -Chris