A Tutorial on the Motorola i50r Basic Telephone Interconnect Repeater Controller

The Motorola i50r is a rather archaic device produced by Motorola in the 1990s for use in controlling simple repeaters while allowing telephone interconnect functionality, remote setup and knockdown of the repeater, and a few other simple functions. It is, in essence, a repeater controller that can be setup in minutes with a few dip switches on the front and runs reliably. Its most important feature is that it provides telephone interconnect or autopatch in a pretty slick and efficient way. Its one big shortcoming is that it lacks an automatic identification feature, so your repeater will be going stealth. (Please refer to FCC or applicable regional rules/regulations regarding the legal operation of your repeater. The axfp.org enterprise is not responsible for your illegal actions while using this device.)


There is perilously little information on the internet for dealing with these. They’re very simple, but my goal here is to consolidate my findings which may prove useful for others using this repeater.

First, setup can be accomplished using dip switches. The table is contained on the repeater-builder website under i50r manual. This configures (among other things) repeater hangtime, availability of the autopatch, audio pass through during autopatch, remote setup/knockdown, power up condition, etc. These dip switches are accessed by removing the front cover of the repeater. There is also a volume potentiometer for adjusting audio levels.

Remote setup and knockdown has been somewhat unclear, and that’s something I’ll clarify here. To accomplish remote setup/knockdown, the i50r basically reads the state of the alarm pin. In order for you to use this feature, the RX radio has to be configured to trigger the alarm pin based on signaling, usually MDC-1200. This means that you need to have an RX radio capable of receiving whatever signaling you wish to use, and a handheld radio capable of transmitting the appropriate signaling.

UPDATE: This is all configured using the Motorola RSS or CPS (depending on your relative vintage of radio). The instructions (lifted from a scan of the service manual) are printed below. It should be pretty straight forward to get it set up, but you’ll need genuine Motorola radios capable of MDC1200 signaling for the RX radio AND the “controlling” portable unit. There’s a whole bundle of menus relating to MDC1200 options in the HT1000 RSS which should get you most of the way error.

Service manual instructions for configuration refer to the RapidCall manuals. I unfortunately don’t have those. But enough fiddling should make this work. See below:


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