pmiller056

Hi Look at the power supply schematic in the first post of topic 'http://www.blue-room.org.uk/index.php?showtopic=59644'. Components R2/R4/C5 (or R3/R5/C7) are required to be fitted at one location (usually the power supply for convenience) to ensure stable operation of the audio part of the system. Your power supply appears to be sufficiently rated - it may not have a big enough output capacitor to cope nicely with the sudden change in load imposed by the signalling system. If not already done, try adding 2200uF/50V (C3 or C4 in the above referenced schematic) electrolytic capacitor to the system to reduce the multiple audio thumps. It may also be useful to add 0.1uF/100nF ceramic or plastic film capacitor at this location too to try and reduce the background whine probably caused by the switch mode power supply unit in use. Regards Peter

Hi I had a look and listen at your video. You will always get a single 'thump' on the audio when the call button is operated/released. Multiple thumps as shown on your video is wrong. Do you have the audio line termination components fitted at the power supply end? Is your power supply adequate? If your power supply is marginal, it may be going into current limit and the output voltage dropping when the call button is operated. This is much more likely if you are using a switch mode power supply (which the background whine suggests you are). Try a different power supply. Regards Peter

Multicomp is the Farnell / CPC / Newark / Element 14 'house brand'. You should be able to get Multicomp branded items from Newark in North America. My experience is that Multicomp parts are fairly generic and sourced from lower cost Asian manufacturers. You should be able to find a branded (but higher cost) equivalent locally. Regards Peter

Why don't you use CTCSS (aka 'tone squelch') tones for the tally signals? Further information at http://en.wikipedia.org/wiki/CTCSS It would be easy to add this signal to the bus and for each receiver to detect their pre-set frequency and put a light on. Good selection of boards, modules and chips to do this are available.... Don't use near multiples of 50Hz (or 60Hz if relevant to you) because the system will be too easily fooled by mains interference. Peter

Thank you. The parts list now makes more sense. Peter

Any chance of a corresponding schematic drawing to go with the published parts list? Thanks Peter