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SRM-5AC asynchronous short range modem from RAD
 SRM-5AC ( SRM5AC/F/RJ45 , SRM5AC/M/RJ45 ) asynchronous short range modem from RAD, is used for local data distribution, connecting full or half duplex asynchronous DTEs to DTEs operating over unconditioned 4-wire lines (two twisted pairs). SRM-5AC ensures integrity of data transmission for distances up to 6.8 km (4.1 miles), depending on wire gauge (see Table 1).
SRM5AC ( SRM5AC/F/RJ45 , SRM5AC/M/RJ45 ) is equipped with an internal filter for high noise immunity. The internal filter overcomes both radiated and conducted interference, and is recommended for noisy environments, such as industrial locations. SRM-5AC ( SRM-5AC/F/RJ45 , SRM5-AC/M/RJ45 ) features a switch-selectable DTE/DCE interface, and a switch-selectable Printer Support Mode. It also includes a jumper for configuring the modem's carrier to be constantly ON or controlled by RTS (see Figure 1 on the data sheet).
When set to DCE, the modem carrier can be set to constantly ON, or controlled by the RTS signal (Circuit 105). Operation
with controlled carrier enables connection of RAD SRM-5AC ( SRM-5AC/F/RJ45/NEW , SRM5-AC/M/RJ45/NEW ) in a multipoint configuration. Controlled carrier can also be used in applications requiring passing of a control signal end-to-end (RTS on one SRM-5-AC is passed to DCD on the other unit). SRM-5AC also includes a LED to indicate carrier detection.
When set to DTE, SRM-5AC ( SRM-5AC/F/RJ45/NEW , SRM5-AC/M/RJ45/NEW ) operates as a DTE for connection to DCE (such as a multiplexer port), without the use of a cross cable.
When set to Printer Support Mode, SRM-5AC supports printer flow control by transmitting DTR on the printer side (busy signal) to CTS on the other side. As a result, CTS at the computer side will drop when the printer becomes busy.
SRM-5AC ( SRM-5AC/F/RJ45/NEW , SRM5-AC/M/RJ45/NEW ) is coupled to the line through isolation transformers, which, in conjunction with additional circuitry, protect against AC or DC overvoltages. As the transformers are rated at over 1,500V RMS, the modem is suitable for connection to local circuits provided by most national telephone administrations.
Innovative circuitry allows SRM-5AC to operate without connection to the mains supply by using ultra-low power from the data and control signals. The modem will operate even if only TD (Circuit 103), RD (Circuit 104) and RTS (Circuit 105) are connected.
The low transmit level minimizes cross talk onto adjacent circuits within the same cable. Data is transmitted and received using a balanced interface, ensuring high immunity to circuit noise.
Two connectors are available for the line connection: a five-screw terminal block, and a modular socket for either RJ-12 or RJ-45
(see Ordering section on the data sheet).
SRM-5AC is fully compatible with SRM-6AC and SRM-6ACU. Additionally, it is compatible with CMN-C6AC and CMN-C6ACU cards for mounting in the CMN-16 compact modem rack.
SRM5ACdata sheet (pdf 735 k)
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