Call and signal machine
The Call and Signal machine ( RSM , in Austria Summer machine ) was dissolved in analog local switching centers , as well as in medium and large analog telephone systems for generating the required AC current of 25 Hz for the ringing voltage and 450 Hz for the call progress tones operated. The RSM is a converter . Since the 1980s, due to the digitization of the telephone system, these signals are no longer generated with electromechanical RSM, but with electronic ringing tone generators.
RSM of the local exchanges
The RSM was an important central component of a switching facility. A failure of the RSM meant that no participants could be called and no audible tones could be sent to the caller. Therefore, larger exchanges always had two redundant RSMs. They were monitored via the generated generator voltage and a standstill contact, so that if the operational RSM failed to run, an immediate switchover to the second RSM took place. The following technical values relate to the situation in Germany.
tasks
- Generation of the 450 Hz audio tones (from System 22 in Germany)
- Generation of the 150 Hz audible tone (was used in the early days of dialer technology as a continuous tone for a busy)
- Generation of the beats for the audible tones (dialing signals, busy signals, override signals)
- Generating the 25 Hz ringing voltage
- Generation of the control cycle for the ringing voltage (10 sec or 5 sec)
- Generating the clocks for other signals (5-min contact)
construction
In the early days, the RSM consisted of a motor for mains operation, a motor for 60 V battery operation, a generator, a gearbox and a signal transmitter. In the later models, there was only a compact version in which the motor and generator are combined in one unit (motor generator). The motor generator uses the 60 V direct current in the exchange to generate the required alternating voltages at 25 Hz. When the machine is idling, the ringing voltage is approx. 75 V to 90 V and under full load approx. 55 V at a frequency of 25 Hz. The alternating voltage of 450 Hz for the audible tones is generated with the help of special windings or a tone wheel. The voltage has a value of approx. 4 to 6 volts. The speed of the machine may be between 1380 and 1620 / min. The limit frequency of the ringing current frequency is set at 23 and 27 Hz and the audio signal frequency is set at 415 and 485 Hz.
The signal transmitter consists of a camshaft and contact sets. The camshaft is coupled to the shaft of the motor generator via the gearbox and actuates the contacts of the contact sets with the cams. This creates the necessary clocks.
The performance of the RSM varies, it was designed according to the size of the exchange.
Guide values:
- 5 VA for OVSt up to 300 AE (connection units)
- 15 VA for OVSt up to 4000 AU
- 60 VA for OVSt over 4000 AU
Signals
Signals towards the caller (all audible tones with 450 Hz):
- Dial tone before September 1979: 200 ms tone, 300 ms pause, 700 ms tone, 800 ms pause ( Morse- A ) →
- Dial tone after September 1979: continuous tone →
- Ring tone: 1000 ms tone, 4000 ms pause →
- Busy tone: 125 ms tone, 475 ms pause →
Signals towards the called party
- Call voltage 60 V, the lowest value mostly up to 90 V with 25 Hz: 1 s call, 4 s pause (older systems 1 s call, 9 s pause)
The instant the first reputation, even Vorruf or FIRST CALL called, was (up to 9 s in older systems) permanent break to avoid the worst case up to 4 seconds immediately after elections at the end turned on and Aufprüfen on the free movement called connection - but not from the RSM , but from the line voter . This so-called "first call" was generated in public switching technology by a slow interrupter (LU) usually consisting of 5 relays. With the System 55, the immediate call was controlled by an NTC thermistor. The next call after the immediate first call was made by the RSM at the specified rate. The contacts are available several times on the RSM and switch one after the other. This distributes the 10 second ringing current to the various line selectors. The RSM is relieved because not all telephones ring at the same time.
The RSM runs continuously in offices with more than 1000 AU, i. H. also at night (continuous operation). In offices with less than 1000 AU, it is mainly shut down during the night and, if necessary, started from the signal frame (start-up operation). Here, the operation of the RSM can either be maintained for the duration of a connection (continuous operation) or limited to the time the audio signals are given (requirement or individual operation). In the first case, the starter relay is switched on in the signal frame when the GW and LW are assigned a contact of the K relay, in the second case it is controlled by a special starter circuit "On" and an on relay of the relevant rack Usually, the RSM is only switched to start-up operation at night; on-demand or individual start-up, on the other hand, is provided as a permanent form of operation in small offices with low traffic.
The call and signal machine had to be given increased attention in the event of a fault. There was an automatic switchover to a second RSM, if available. The switchover is triggered by a standstill contact. A failure of the RSM is synonymous with failure of the entire exchange. Therefore, in the event of a failure, the main alarm (rattle alarm clock, blue lamp) was triggered immediately. Until the electromechanical exchanges were dismantled, no electronic replacement was planned for the RSM - so the RSM howled to themselves with their unmistakable noise in the frame until the last, electromechanical local exchange 55v was closed.
RSM in private branch exchanges
In private branch exchanges , the RSM were mostly of a similar design, depending on the size of the system, the audible tones and signals generated were almost identical with the exception of the dial tone (here mostly a Morse-S).
See also
Individual evidence
literature
- Handheld electrical telecommunications dictionary . 2nd edition, 3rd volume Q-Z, p. 1433